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Sensitivity Constraints of Extractive Electrospray for a Model System and Secondary Organic Aerosol
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Analytical Chemistry

Cite this: Anal. Chem. 2023, 95, 37, 13788–13795
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https://doi.org/10.1021/acs.analchem.3c00441
Published September 1, 2023

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Abstract

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The quantification of an aerosol chemical composition is complicated by the uncertainty in the sensitivity of each species detected. Soft-ionization response factors can vary widely from molecule to molecule. Here, we have employed a method to separate molecules by their volatility through systematic evaporation with a thermal denuder (TD). The fraction remaining after evaporation is compared between an extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF) and a scanning mobility particle sizer (SMPS), which provides a comparison between a quantified mass loss by the SMPS and the signal loss in the EESI-TOF. The sensitivity of the EESI-TOF is determined for both a simplified complex mixture (PEG-300) and also for a complex mixture of α-pinene secondary organic aerosol (SOA). For PEG-300, separation is possible on a molecule-by-molecule level with the TD and provides insights into the molecule-dependent sensitivity of the EESI-TOF, showing a higher sensitivity toward the most volatile molecule. For α-pinene SOA, sensitivity determination for specific classes is possible because of the number of molecular formula observed by the EESI-TOF. These classes are separated by their volatility and are broken down into monomers (O3–5,6–7,8+), dimers (O4–7,8+), and higher order oligomers (e.g., trimers and tetramers). Here, we show that the EESI-TOF initially measures 60.1% monomers, 32.7% dimers, and 7.2% trimers and tetramers in α-pinene SOA, but after sensitivity correction, the distribution of SOA is 37.4% monomers, 56.1% dimers, and 6.4% trimers and tetramers. These results provide a path forward for the quantification of aerosol components with the EESI-TOF in other applications and potentially for atmospheric measurements.

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Subjects

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Aerosols are particles suspended in air with diameters spanning from the nanometer to micrometer range. (1) Aerosols are used for drug delivery, (2) but can be detrimental to human health when they include toxic components (e.g., PAHs, non-exhaust traffic emissions, dust, etc.). (3) For both cases, it is important to measure and quantify the chemical components present in the aerosol. (4) Quantification is particularly difficult for atmospheric organic aerosol (OA), which makes up 20–90% of atmospheric aerosol. (5) A mixture of directly emitted molecules and species formed from gas-phase oxidation reactions make up the composition of OA. Reactions of emitted molecules with atmospheric oxidants can yield thousands of different product molecules, (6,7) making quantification with standards an impossible task. Oxidation products can vary significantly in their composition, ranging from low-molecular-weight monomers to high-molecular-weight oligomers (e.g., dimers, trimers, tetramers, etc.). Oligomeric content has been shown to be an important contribution of OA generated in laboratory studies, (8) but quantification of these products are lacking. Therefore, the importance of oligomers in both laboratory studies and the atmosphere remains uncertain.
Harsh electron impact ionization provides quantitative analysis, but in the complex matrix of OA, electron impact techniques cannot provide molecular information. Soft ionization techniques that include chemical ionization methods (e.g., I–, NO3–, NH4+, H3O+, etc.), (6,9,10) droplet assisted ionization, and extractive electrospray ionization (4,11−14) afford detailed chemical resolution, but sensitivity can vary dramatically from molecule to molecule. (4,11,15) The EESI technique is a soft ionization method with sensitivity toward organic molecules sufficient for atmospheric measurements (ng m–3 detection limits). (13,14,16,17) In these studies, the electrospray working solution (water or water/acetonitrile mix) was doped with NaI to promote Na+ adduct formation and detects molecules that are soluble and have strong binding energies to Na+. Though, some fragmentation appears to occur when both hydroxynitrates or nitrate functional groups are present, (17,18) and other potential artifacts (e.g., reactions) are observed in ESI experiments, (19) but have not been detected within EESI measurements of OA to date.
In pursuit of quantitative analysis from soft ionization techniques, recent studies have constrained the instrument response to a given analyte according to its binding energy to adducts in chemical ionization techniques, which is in turn estimated from the analyte’s molecular formula. Gas-particle partitioning has also been attempted as a way to constrain the response factor for the extractive electrospray ionization when compared against a proton-transfer reaction mass spectrometer (PTR-MS) measuring gas-phase species. (4) This study used a seed aerosol to encourage partitioning of gaseous molecules to the particle phase, but was only sensitive to species the PTR-MS could measure and those that would partition to the aerosol phase. Thus, the predominant species measured were smaller molecules predominantly found in the gas-phase, with no molecules larger than 300 m/z reported. Thus, a significant gap exists in determining the response to oligomeric species and their quantification remains uncertain.
In this study, we provide a new approach to quantify the measured EESI-TOF composition. Here, the EESI-TOF response is compared against bulk organic mass concentration measured by a scanning mobility particle sizer (SMPS) for mixtures of quasi-known species (PEG-300) and a complex mixture of α-pinene SOA. PEG-300 is a group of molecules that spans a wide range in both mass and volatility, and is a common set of molecules used for instrument calibrations. (20) The EESI-TOF sensitivity toward classes of compounds with different volatilities is assessed by systematically removing molecules from the aerosol phase via evaporation using a thermal denuder (TD). The technique developed here will be beneficial for the quantification of molecular groups in different complex aerosol mixtures, potentially including in ambient environments or industrial applications, and can be applied to aerosol mass spectrometers other than the EESI-ToF.

Experimental Section

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Laboratory experiments were conducted with both the individual model compounds PEG 5, 6, 8, 10, and 12 and the mixture of PEG-300, and an experimental setup can be found in Figure S1. The solutions were aerosolized using a home-built nebulizer, creating aerosols that were subsequently dried. PEG-300 was introduced to a TD (Aerodyne), with 1.3 L min–1 sampled into the TD and the excess flow exhausted. After the TD, a multi-channel charcoal denuder was installed to remove the gas-phase species that evaporate during heating. Finally, the particles were sampled by the EESI-TOF and a scanning mobility particle sizer (SMPS, TSI Inc. model 3938, 3 L min–1 sheath and 0.3 L min–1 sample). The condensation particle counter (CPC) used was compared against an ACTRIS standard CPC and agreed within ±2%. The SMPS was calibrated with a series of polystyrene latex spheres, and agreed well with the manufacturers specifications. The aerosol mass was determined using the assumed particle density of PEG-300 (1.13 g cm–3) or α-pinene SOA (1.2 g cm–3). (21,22) Similar particles have been measured previously and were shown to be spherical, removing possible uncertainties in the aerosol mass measurement. (22) The multiple charge correction inversion creates the largest uncertainty in the SMPS measurement and is on the order of ∼10%; therefore, the absolute error on the mass measurement of the SMPS will be on the order of ∼15%. The temperature of the TD was systematically increased from low to high temperatures during the course of the experiment. Experiments with nebulizers had relatively constant aerosol concentrations (±5%). The residence time in the TD varied from 7 s at 20 °C to 3.5 s at 175 °C.
Secondary organic aerosol experiments were performed in a 9 m3 atmospheric simulation chamber, described previously. (23) In the experiments presented here, α-pinene SOA was produced by reacting 100 ppb of α-pinene with ∼1000 ppb of O3. High concentrations of O3 were utilized to reach maximum aerosol concentrations within the first 3–5 min after α-pinene injection. In chamber experiments, the particles were sampled either directly from the chamber to the instruments (SMPS, and EESI-TOF) or passed through a longer line including the TD with a multi-channel denuder on the output. The time series were corrected for both chamber dilution and wall loss of particles in the chamber using the same method reported previously. (10,13)
A subset of measurements was performed with an Orbitrap mass spectrometer (Thermo Fisher, Exploris 120). A PEG-300 solution was nebulized, dried using a Nafion dryer and subsequently introduced into an Orbitrap, equipped with a custom build EESI inlet. MS/MS was carried out for each PEG from 5 to 12, with the collision energy ranging from 1 to 40 eV. Signal at 1 eV was used to normalize the results.

Extractive Electrospray Ionization Mass Spectrometry

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The EESI was connected to an atmospheric pressure time-of-flight mass spectrometer (Tofwerk) with a resolution of either 5000 ΔM/M (PEG experiments) or 10,500 ΔM/M (smog chamber experiments). The aerosol was passed through a series of switching valves oscillating between a sampling line (5 min) and a HEPA filter (1 min) to continually obtain background measurements. After the series of switching valves, a multi-channel denuder stripped the gas-phase components, ensuring the EESI only encountered the aerosols. The electrospray capillary operated at 2.9 kV with a backing pressure of 0.2 bar with a working solution of 100 ppm NaI in purified water (MilliQ). The inlet to the mass spectrometer consisted of a metal inlet capillary that was typically heated to 270 °C, except for a single PEG-300 experiment at 110 °C. Thermocouples were connected to different points on the EESI inlet (see Figure S2) to assess the temperatures encountered by the particles on entering the instrument. The higher inlet capillary temperature resulted in an EESI temperature of 40 °C (at Figure S2: P2) and an inlet tube temperature (Figure S1: P1) of 35–40 °C, while for the lower inlet capillary temperature (110 °C) both P1 and P2 were 22 °C. The data were analyzed using Tofware v3.2.3. In the experiments with standards and PEGs, all peaks were assigned according to their known polymeric molecular formulae. For α-pinene SOA, peaks could be effectively assigned to species below m/z 500; however, the mass spectrometer resolution prevented conclusive assignments above m/z 500. However, there are significant contributions to the aerosol signal present above m/z 500 and these data are used to determine the signal associated with trimers and tetramers, as discussed below in the Results section. The data are obtained as ions s–1, which were converted to ag s–1 by the following
EESI(ags−1)x=EESI(#s−1)x·MWx×10186.023×1023
(1)
where EESI (# s–1)x is the measured EESI signal of ion x in s–1, MWx is the molecular weight of x, Avogadro’s number converts molecules into mole, and 1018 converts grams into attograms (ag).

Results

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Separating Sensitivity in an Ideal Complex Mixture

PEGs span a wide range of molecular weights, shown in Figure 1A. PEGs are detected as C2nH4n+2On+1Na+ because of adduct formation with Na+ in the electrospray solution, and are observed to span n = 5–16 by the EESI-TOF ranging from 261 to 745 m/z. A majority (99+%) of the signals shown in Figure 1A represent PEG-Na+ adducts. The range of masses shown in Figure 1A delivers a useful range over which to assess the sensitivity of the EESI-TOF as a function of the molecular weight of species containing the same functional groups.

Figure 1

Figure 1. (A) Mass spectrum of PEG-300 as measured by the EESI. (B) Fraction remaining of each PEG measured by the EESI as a function of TD temperature, from triplicates. (C) A single measurement showing absolute mass concentration (left-axis) measured by the SMPS, EESI mass flux (red axis, right side), and for the EESI sensitivity using the mid-point temperatures (blue axis, right side), and the error bars correspond to the error propagated using the measured standard error.

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To isolate the sensitivity on a molecule-by-molecule basis, a TD was used to selectively evaporate molecules based on their saturation vapor concentration (or volatility). The method requires the EESI-TOF to be used in conjunction with a quantitative reference instrument (here, the SMPS is used) because the SMPS provides a quantitative measure of the mass concentration (μg m–3) of organics present, while the EESI measures the different molecular formula of species remaining after evaporating the most volatile fraction from the aerosol. Figure 1B shows the relative fraction remaining as a function of TD temperature as measured by the EESI-TOF, and highlights the ability to separate specific molecules from the complex mixture of PEG-300 as a function of TD temperature.
Figure 1C shows the change in the total EESI signal and the measured mass by the SMPS, as a function of temperature (size distributions are shown in Figure S3). There are distinct differences in the temperature dependence exhibited by all measurements, with the EESI undergoing an initial large drop in intensity between 20 and 30 °C, followed by evaporation that appears delayed relative to the SMPS, and matching the SMPS again above 100 °C.
Figure 1C also shows the bulk sensitivity for the EESI (ag s–1)/(μg m–3), determined by comparing the change in total EESI signal (ag s–1) to the change in mass measured by the SMPS, as follows
sensitivitybulk=∑EESI(T1)i−∑EESI(T2)iSMPSmass(T1)−SMPSmass(T2)
(2)
where T1 and T2 are the adjacent TD temperature setpoints, the SMPS mass is the average mass concentration over the measurement period, and EESI (Tx) is the summed EESI signal for all measured components at a specific temperature. Here, we define the sensitivity in terms of the fraction that is evaporating from the aerosol phase in eq 2.
As shown in Figure 1C, the bulk sensitivity varies considerably as a function of volatility. The sensitivity initially decreases dramatically because there is virtually no change in the signal of the SMPS, while the EESI observes a 15% decrease in signal between 20 and 30 °C. These changes are associated with evaporation of the most volatile PEG (n = 5, C10H22O5), which fully evaporates by 40 °C and is detected with unusually high sensitivity. With the increase in temperature, the sensitivity decreases, reaching a minimum between 35 and 50 °C, where PEG-6 (C12H26O6) was the predominant species evaporating. The sensitivity then increased for the larger molecules from 10 to 30 (ag s–1)/(μg m–3). Figure S4 shows the dominant species evaporating between each temperature step. Where a specific PEG made up 50+% of the evaporating fraction, the sensitivity derived from taking an average of the bulk method (shown in Figure 1C) was used as an initial assessment of its sensitivity, shown in Figure 2A. For PEG-10 and 11, the initial sensitivity was determined where they evaporated the most. The initial guess was fed into an iterative solver using eq S1 to refine the sensitivity, described in the Supporting Information. Both the initial assessment and the result from the iterative solution for assessment are shown in Figure 2A, and generally agree.

Figure 2

Figure 2. (A) EESI sensitivity determined from bulk standards compared to the bulk TD method and iterative-TD sensitivities (left-axis). Binding energies are shown for each PEG (right-axis). (B) Composition of PEG-300 without correction (blue) compared to the composition after correction based on EESI sensitivity (orange).

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To assess the validity of the sensitivity determined in Figure 2A, a subset of the individual PEG molecules were measured with both the EESI and SMPS. The size distributions in all cases were similar with a peak in the volume-weighted distribution ∼100 nm. The range of sensitivities reported in Figure 2A from the TD-EESI measurements (both bulk and iterative method) agrees well with the sensitivity measured when directly atomizing known species, providing confidence that the TD-EESI method can determine the sensitivity of unknown mixtures.
The variability in the sensitivity in Figure 2A exhibits both high sensitivity at low TD temperatures and a steadily increasing sensitivity with temperature for larger molecules. The steadily increasing trend in Figure 1C from 40 to 120 °C may relate to the increased binding energy of Na+ to large molecules, which can more efficiently form bonds with the Na+ stabilizing the adduct. The binding energy of Na+ to ethers (e.g., dimethyl ether, crown ethers, etc.) increases with the number of ether groups present on the molecule. (24) The increased binding energy was experimentally verified using MS/MS measurements performed on PEG-300 (right-axis on Figure 2A). While the increase in the binding energy of the PEG-Na+ adducts explains the trend in sensitivity at temperatures >40 °C, the outsized sensitivity of PEG5, which evaporates <40 °C, remains unexplained. We measured the temperature of the EESI inlet to be 42 °C in the spray region and 37 °C in the tube leading to the spray, both of which are above room temperature. Therefore, this region likely facilitates evaporation of the most volatile components such as PEG-5. Because the EESI has considerably higher sensitivity toward the gas-phase compared to the particle phase, thereby explaining the higher sensitivity of PEG-5. (25) To test this hypothesis, experiments were performed in which the temperature of the inlet capillary was lowered from 275 to 110 °C, thereby decreasing the temperature on the EESI inlet to room temperature. When PEG-300 was passed through the TD at 30–40 °C the sensitivity of the PEG5 decreased to ∼5 (ag s–1)/(μg m–3).
The mass spectrum shown in Figure 1A represents the measurements of the EESI toward PEG-300 without any correction for the variation in sensitivity observed. Given the dependence of sensitivity on molecular identity in Figure 1B, it is clear that applying a single bulk sensitivity does not properly represent the composition of PEG-300. Averaged sensitivities shown in Figure 2A (iterative solution) are applied to the EESI data, converting ag s–1 into μg m–3 of each component present. Figure 2B shows the relative faction of each PEG unit before and after the correction, increasing the contribution of the lowest sensitivity species (PEG-6 and 7) while decreasing the contribution to the rest of the distribution. Furthermore, after the correction, the agreement with the measured mass improves, as shown in Figure S5.

Application to Secondary Organic Aerosol

Here, we apply the method for quantification of volatility-resolved fractions of PEG-300 to a complex atmospherically relevant organic aerosol. Secondary organic aerosol (SOA) was chosen as a mixture of complex unknown species because SOA is generated by oxidation reactions that produce a wide range of chemical species, akin to an organic chemistry experiment gone awry, as clearly illustrated in Figure 3A. Additionally, SOA should mostly comprise water-soluble species detectable by the EESI, rendering differences in extraction efficiency negligible. (26) Figure 3B shows a mass defect plot of α-pinene SOA generated via ozonolysis. The groups of ions in Figure 3B with a negative mass defect that continues to decrease with m/z correspond to [M]NaxIx–1+ clusters; these have signals that are orders of magnitude lower than the typical [M]Na+ adducts and are removed from further analysis. For the remaining ([M]Na+) ions, Figure 3B clearly shows regions corresponding to monomers, dimers, trimers (orange box), and tetramers (green box). Given the range of molecules present, they may be differentiated by volatility, and their relative sensitivities assessed.

Figure 3

Figure 3. (A) Mass spectrum from α-pinene SOA measured by the EESI. (B) Mass defect plot of the same mass spectrum. Trimers highlighted in orange, tetramers highlighted in green.

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The composition of SOA directly measured by the EESI is shown in Figure S4, where it is classified in terms of carbon and oxygen. Monomers comprise 60% of the signal, dimers 32.7%, trimers 6.2%, and tetramers 1.0%. Passing the SOA through the TD results in selective evaporation of volatility-segregated classes of SOA components. Molecular formulae were aggregated according to their evaporation behavior (shown in Figure S5A,B). The classes are split into monomers (C7–10) and dimers (C15–20), and further aggregated according to the number of oxygen atoms present (e.g., C7–10HxO3–5,6–7,8+ and C15–20HyO4–7,10+). Figure 4A shows each class of molecules and the temperature-dependent evaporation of the aggregated molecular species. Between 20 and 70 °C, monomers evaporate from the particle phase, with those having the fewest oxygens evaporating at the lowest temperatures. The distinction between C7–10HxO3–5 and C7–10HxO6,7 is not straightforward since both classes of molecules predominately evaporate between 20 and 55 °C. However, the C7–10HxO6,7 class evaporates at systematically higher temperatures and have a much larger fraction evaporating between 55 and 70 °C. Dimers evaporate between 70 and 125 °C, again with higher oxygen number corresponding to higher evaporation temperatures. Trimers and tetramers mostly evaporate above 125 °C. These results show that the dimers, trimers, and tetramers are effectively the only species left in the particle phase after 70–85 °C meaning that ∼50% of the aerosol must be oligomers based on Figure 4A.

Figure 4

Figure 4. (A) Fraction remaining of the SMPS mass concentration (size distributions are found in Figure S7), EESI measured composition, and aggregated classes of α-pinene SOA (from triplicate measurements). (B) Relative fraction of species evaporating between TD steps for a single measurement.

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The comparison between the total EESI signal and the SMPS for SOA (Figure 4A), shows that the EESI signal does not perfectly follow the aerosol mass concentration in response to evaporation, with the discrepancies consistent with those observed for PEG-300. Using Figure 4A, the positive bias in the EESI again comes from the most volatile species (less oxygenated monomers) evaporating due to high inlet capillary temperatures and low volatile species (trimers and tetramers), while the negative bias is centered on highly oxygenated monomers and dimers. The relatively good separation in the evaporation temperatures between the major molecular classes (e.g., C7–10HxO3–5 and C15–20HyO8+) facilitates quantification of their sensitivities by comparison with SMPS, analogous to the PEG experiments, which will more accurately determine the oligomeric fraction. Based on the chosen classes, the highly oxygenated monomers (C7–10HxO8+) and low oxygenated dimers (C15–20HxO4–7) were aggregated for the sensitivity determination, but are shown as separate species below.
As done for PEG, the availability of volatility-resolved sensitivities provides a means of correcting the measured carbon distribution. The bulk method was used to generate an initial guess of the sensitivity of the molecular classes of α-pinene SOA, and an iterative approach was used to refine the sensitivity (as described in the Supporting Information and used for PEG-300). For molecular classes that dominated an individual evaporation period (C7HxO3–5, C15–20HyO8+, and trimers), the bulk sensitivity during that period was taken as an initial guess in the model. Otherwise, the model was initialized using the temperature range in which molecular classes exhibited the most evaporation (40–70 °C for C7–10HxO6,7; 55–85 °C for C7–10HxO8+/C15–20HyO4–7). Figure 5A includes the determined sensitivity for each molecular class (including the initial guess for comparison) using this method, in the units of (ag sec–1)/(μg m–3). Figure 5B highlights the change in the relative contributions of the different molecular classes using the iterative correction in Figure 5A. The species which did not dominate the evaporation in any specific period had relatively large errors, and results in the large error bars in Figure 5B. When shown as EESI mass concentration after sensitivity correction, there is good agreement with the measured SMPS mass concentration (Figure S8) and largely falls on the 1:1 line.

Figure 5

Figure 5. (A) Sensitivity for the different molecular classes of α-pinene SOA based on bulk sensitivities (initial guess) and after the iterative solution. (B) Relative contribution of each molecular class before and after the sensitivity correction using the iterative solution.

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The sensitivity correction in Figure 5B increases the contribution of dimers and highly oxygenated monomers (On≥6) relative to all other components of the SOA. In terms of relative abundance, the correction based on sensitivity decreased the monomer fraction from 60.2 to 37.4%, increased the dimers from 32.7 to 56.1%, and decreased the higher order oligomers from 7.2 to 6.4%. The estimated fractions of oligomers are consistent with the simple view in Figure 4A, where oligomers are ∼50% of the aerosol. After using the iterative approach, the fractions of oligomers are greater than the rough estimate because low oxygenated dimers are beginning to evaporate between 55 and 70 °C. Changes to the less oxygenated monomers (C7–10HxO3–5) drives the large decrease in the relative intensity of the monomer distribution (Figure 5B), while all dimer classes are enhanced with the correction. Overall, the correction fundamentally changes the picture of the composition of α-pinene SOA from one dominated by monomers to one where dimers are the most important contributor to the SOA mass. Previously, oligomers (dimers, trimers, tetramers, etc.) have been observed in atmospheric gas-phase and particle-phase measurements, (10,13,17,27) but no method assigned bulk concentrations of oligomers in SOA until now.

Discussion

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The combination of the TD in conjunction with the EESI provides important information and constraints on the bulk quantification of organic aerosol components. Using the TD as a means to remove specific classes of molecules provides constraints on the sensitivity of these molecular classes without the need to generate specific standards associated to each molecule. Here, we use this method to extract information about the sensitivity of the EESI toward readily purchased molecules, and then expand the analysis to a mixture of unknown species using laboratory-generated SOA. This provides a basis for probing the variability in aerosol composition across OA from different sources and precursors. This method can be applied to systems for molecular sensitivities when there is not significant overlap in the volatility, as we show in the case of PEG-300. The alternative for complex systems (e.g., α-pinene SOA) is to separate species into volatility-based classes; this does not provide direct sensitivity on a molecule-by-molecule basis, but provides a generalized class sensitivity. The method cannot rule out the possibility that the sensitivity of individual molecules may vary considerably within a given volatility-based class. Despite this limitation, we show here this method can be used to provide important quantitative insights into SOA composition, such as the oligomeric fraction of α-pinene SOA. Overall, these results demonstrate the importance of dimers on the overall composition of α-pinene SOA and prescribe a method with which to correct for sensitivity differences among the different components of OA. Many studies have shown that oligomers are important constituents of SOA, (8) but no study has been able to quantify this fraction.
It is also important to note that the use of SMPS-measured evaporated mass as reference means that this method is only applicable to complex mixtures consisting of species that are water soluble and readily binding to Na+. In the atmosphere, there are aerosol components that the EESI may not ionize (e.g., hydrocarbon-like organic aerosol), which would render this method inoperable. The good agreement between the binding energy of the PEGs and EESI sensitivity derived from both the single components and TD-EESI method could provide a way forward to determine the EESI sensitivity on a molecule-by-molecule basis. Empirical determination of binding energies through collision induced dissociation measurements could provide a means to determine EESI sensitivity, and will be explored further in subsequent flow tube and chamber measurements. Though, this needs to be systematically determined with known species rather than complex mixtures because the binding energies likely varies based on the carbon backbone of the molecule, as shown for isomers for both α-pinene SOA and trimethyl benzene SOA. (4)
The TD-EESI combination additionally provides the possibility to model the volatility and saturation vapor concentrations of the molecules observed, however, the scope of this paper is to highlight its use to constrain the sensitivity of the EESI toward monoterpene SOAs. Future work will include extracting the volatility parameters on a molecule-by-molecule basis. Additionally, this method will be applied to the broad differences in the composition arising from different monoterpene SOAs.

Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.analchem.3c00441.

  • Description of iterative solution for sensitivity, experimental design, schematic of the EESI inlet, average size distributions measured by the SMPS for PEG-300, fraction evaporating from PEG-300 for each specific species, comparison of the EESI mass concentrations with sensitivity conversion (in Figure 2A) from ag s-1 to μg m-3 to the measured SMPS mass concentration, fraction remaining of the monomer and dimer regions aggregated by oxygen number as a function of TD temperature, mass weighted size distributions, and mass concentration comparison (PDF)

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Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.

Author Information

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  • Corresponding Author
  • Authors
    • Jun Zhang - Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, Villigen 5232, Switzerland
    • Jens Top - Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, Villigen 5232, Switzerland;  Orcidhttps://orcid.org/0000-0003-3318-4451
    • Sophie Bogler - Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, Villigen 5232, Switzerland
    • Mihnea Surdu - Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, Villigen 5232, Switzerland;  Orcidhttps://orcid.org/0000-0003-1815-2750
    • Jay G. Slowik - Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, Villigen 5232, Switzerland
    • Andre S. H. Prevot - Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, Villigen 5232, Switzerland;  Orcidhttps://orcid.org/0000-0002-9243-8194
    • Imad El Haddad - Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, Villigen 5232, Switzerland;  Orcidhttps://orcid.org/0000-0002-2461-7238
  • Author Contributions

    D.M.B. wrote the manuscript with contributions from all authors. D.M.B., J.Z., M.S., and J.T. performed chamber experiments. J.Z. and S.B. performed PEG measurements. D.M.B. and J.Z. analyzed the EESI data. J.T. performed collision-induced dissociation measurements. All authors gave approval to the final version of the manuscript.

  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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This work was supported by the Swiss National Science Foundation (grant 09802.01.03, 200021_213071, 206021_198140, and 200020_188624) as well as the European Union’s Horizon 2020 research and innovation programme through the ATMO-ACCESS Integrating Activity under grant agreement no. 101008004 and the Marie Curie doctoral network under grant no. HORIZON-MSCA-2021-DN-01.

References

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    Koop, Thomas; Bookhold, Johannes; Shiraiwa, Manabu; Poeschl, Ulrich
    Physical Chemistry Chemical Physics (2011), 13 (43), 19238-19255CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
    Recently, it has been proposed that org. aerosol particles in the atm. can exist in an amorphous semi-solid or solid (i.e. glassy) state. In this perspective, we analyze and discuss the formation and properties of amorphous semi-solids and glasses from org. liqs. Based on a systematic survey of a wide range of org. compds., we present ests. for the glass-forming properties of atm. secondary org. aerosol (SOA). In particular we investigate the dependence of the glass transition temp. Tg upon various mol. properties such as the melting temp., their molar mass, and their at. oxygen-to-carbon ratios (O : C ratios) of the compds. Also the effects of mixing different compds. and the effects of hygroscopic water uptake depending on ambient relative humidity are investigated. In addn. to the effects of temp., we suggest that molar mass and water content are much more important than the O : C ratio for characterizing whether an org. aerosol particle is in a liq., semi-solid, or glassy state. Moreover, we show how the viscosity in liq., semi-solid and glassy states affect the diffusivity of those mols. constituting the org. matrix as well as that of guest mols. such as water or oxidants, and we discuss the implications for atm. multi-phase processes. Finally, we assess the current state of knowledge and the level of scientific understanding, and we propose avenues for future studies to resolve existing uncertainties.
    (b) Shiraiwa, M.; Ammann, M.; Koop, T.; Pöschl, U. Gas uptake and chemical aging of semisolid organic aerosol particles. Proc. Natl. Acad. Sci. U.S.A. 2011, 108, 11003– 11008,  DOI: 10.1073/pnas.1103045108
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    1b
    Gas uptake and chemical aging of semisolid organic aerosol particles
    Shiraiwa, Manabu; Ammann, Markus; Koop, Thomas; Poschl, Ulrich
    Proceedings of the National Academy of Sciences of the United States of America (2011), 108 (27), 11003-11008, S11003/1-S11003/7CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)
    Org. substances can adopt an amorphous solid or semisolid state, influencing the rate of heterogeneous reactions and multiphase processes in atm. aerosols. Here we demonstrate how mol. diffusion in the condensed phase affects the gas uptake and chem. transformation of semisolid org. particles. Flow tube expts. show that the ozone uptake and oxidative aging of amorphous protein is kinetically limited by bulk diffusion. The reactive gas uptake exhibits a pronounced increase with relative humidity, which can be explained by a decrease of viscosity and increase of diffusivity due to hygroscopic water uptake transforming the amorphous org. matrix from a glassy to a semisolid state (moisture-induced phase transition). The reaction rate depends on the condensed phase diffusion coeffs. of both the oxidant and the org. reactant mols., which can be described by a kinetic multilayer flux model but not by the traditional resistor model approach of multiphase chem. The chem. lifetime of reactive compds. in atm. particles can increase from seconds to days as the rate of diffusion in semisolid phases can decrease by. multiple orders of magnitude in response to low temp. or low relative humidity. The findings demonstrate that the occurrence and properties of amorphous semisolid phases challenge traditional views and require advanced formalisms for the description of org. particle formation and transformation in atm. models of aerosol effects on air quality, public health, and climate.
  2. 2
    (a) Dolovich, M. B.; Dhand, R. Aerosol drug delivery: developments in device design and clinical use. Lancet 2011, 377, 1032– 1045,  DOI: 10.1016/S0140-6736(10)60926-9
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    2a
    Aerosol drug delivery: developments in device design and clinical use
    Dolovich, Myrna B.; Dhand, Rajiv
    Lancet (2011), 377 (9770), 1032-1045CODEN: LANCAO; ISSN:0140-6736. (Elsevier Ltd.)
    A review. Summary: Aerosolised drugs are prescribed for use in a range of inhaler devices and systems. Delivering drugs by inhalation requires a formulation that can be successfully aerosolised and a delivery system that produces a useful aerosol of the drug; the particles or droplets need to be of sufficient size and mass to be carried to the distal lung or deposited on proximal airways to give rise to a therapeutic effect. Patients and caregivers must use and maintain these aerosol drug delivery devices correctly. In recent years, several tech. innovations have led to aerosol drug delivery devices with efficient drug delivery and with novel features that take into account factors such as dose tracking, portability, materials of manuf., breath actuation, the interface with the patient, combination therapies, and systemic delivery. These changes have improved performance in all four categories of devices: metered dose inhalers, spacers and holding chambers, dry powder inhalers, and nebulisers. Addnl., several therapies usually given by injection are now prescribed as aerosols for use in a range of drug delivery devices. In this Review, we discuss recent developments in the design and clin. use of aerosol devices over the past 10-15 years with an emphasis on the treatment of respiratory disorders.
    (b) Douafer, H.; Andrieu, V.; Brunel, J. M. Scope and limitations on aerosol drug delivery for the treatment of infectious respiratory diseases. J. Controlled Release 2020, 325, 276– 292,  DOI: 10.1016/j.jconrel.2020.07.002
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    2b
    Scope and limitations on aerosol drug delivery for the treatment of infectious respiratory diseases
    Douafer, Hana; Andrieu, Veronique; Brunel, Jean Michel
    Journal of Controlled Release (2020), 325 (), 276-292CODEN: JCREEC; ISSN:0168-3659. (Elsevier B.V.)
    A review. The rise of antimicrobial resistance has created an urgent need for the development of new methods for antibiotics delivery to patients with pulmonary infections in order to mainly increase the effectiveness of the drugs administration, to minimize the risk of emergence of resistant strains, and to prevent patients reinfection. Since bacterial resistance is often related to antibiotic concn., their pulmonary administration could eradicate strains resistant to the same drug at the concn. achieved through the systemic circulation. Pulmonary administration offers several advantages; it directly targets the site of the infection which allows the inhaled dose of the drug to be reduced compared to that administered orally or parenterally while keeping the same local effect. The review article is made with an objective to compile information about various existing modern technologies developed to provide greater patient compliance and reduce the undesirable side effect of the drugs. In conclusion, aerosol antibiotic delivery appears as one of the best technologies for the treatment of pulmonary infectious diseases and able to limit the systemic adverse effects related to the high drug dose and to make life easier for the patients.
  3. 3
    Daellenbach, K. R.; Uzu, G.; Jiang, J.; Cassagnes, L.-E.; Leni, Z.; Vlachou, A.; Stefenelli, G.; Canonaco, F.; Weber, S.; Segers, A. Sources of particulate-matter air pollution and its oxidative potential in Europe. Nature 2020, 587, 414– 419,  DOI: 10.1038/s41586-020-2902-8
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    3
    Sources of particulate-matter air pollution and its oxidative potential in Europe
    Daellenbach, Kaspar R.; Uzu, Gaelle; Jiang, Jianhui; Cassagnes, Laure-Estelle; Leni, Zaira; Vlachou, Athanasia; Stefenelli, Giulia; Canonaco, Francesco; Weber, Samuel; Segers, Arjo; Kuenen, Jeroen J. P.; Schaap, Martijn; Favez, Olivier; Albinet, Alexandre; Aksoyoglu, Sebnem; Dommen, Josef; Baltensperger, Urs; Geiser, Marianne; El Haddad, Imad; Jaffrezo, Jean-Luc; Prevot, Andre S. H.
    Nature (London, United Kingdom) (2020), 587 (7834), 414-419CODEN: NATUAS; ISSN:0028-0836. (Nature Research)
    Abstr.: Particulate matter is a component of ambient air pollution that has been linked to millions of annual premature deaths globally1-3. Assessments of the chronic and acute effects of particulate matter on human health tend to be based on mass concn., with particle size and compn. also thought to play a part4. Oxidative potential has been suggested to be one of the many possible drivers of the acute health effects of particulate matter, but the link remains uncertain5-8. Studies investigating the particulate-matter components that manifest an oxidative activity have yielded conflicting results7. In consequence, there is still much to be learned about the sources of particulate matter that may control the oxidative potential concn.7. Here we use field observations and air-quality modeling to quantify the major primary and secondary sources of particulate matter and of oxidative potential in Europe. We find that secondary inorg. components, crustal material and secondary biogenic org. aerosols control the mass concn. of particulate matter. By contrast, oxidative potential concn. is assocd. mostly with anthropogenic sources, in particular with fine-mode secondary org. aerosols largely from residential biomass burning and coarse-mode metals from vehicular non-exhaust emissions. Our results suggest that mitigation strategies aimed at reducing the mass concns. of particulate matter alone may not reduce the oxidative potential concn. If the oxidative potential can be linked to major health impacts, it may be more effective to control specific sources of particulate matter rather than overall particulate mass.
  4. 4
    Wang, D. S.; Lee, C. P.; Krechmer, J. E.; Majluf, F.; Tong, Y.; Canagaratna, M. R.; Schmale, J.; Prévôt, A. S. H.; Baltensperger, U.; Dommen, J. Constraining the response factors of an extractive electrospray ionization mass spectrometer for near-molecular aerosol speciation. Atmos. Meas. Tech. 2021, 14, 6955– 6972,  DOI: 10.5194/amt-14-6955-2021
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    4
    Constraining the response factors of an extractive electrospray ionization mass spectrometer for near-molecular aerosol speciation
    Wang, Dongyu S.; Lee, Chuan Ping; Krechmer, Jordan E.; Majluf, Francesca; Tong, Yandong; Canagaratna, Manjula R.; Schmale, Julia; Prevot, Andre S. H.; Baltensperger, Urs; Dommen, Josef; El Haddad, Imad; Slowik, Jay G.; Bell, David M.
    Atmospheric Measurement Techniques (2021), 14 (11), 6955-6972CODEN: AMTTC2; ISSN:1867-8548. (Copernicus Publications)
    Online characterization of aerosol compn. at the near-mol. level is key to understanding chem. reaction mechanisms, kinetics, and sources under various atm. conditions. The recently developed extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF) is capable of detecting a wide range of org. oxidn. products in the particle phase in real time with minimal fragmentation. Quantification can sometimes be hindered by a lack of available com. stds. for aerosol constituents, however. Good correlations between the EESI-TOF and other aerosol speciation techniques have been reported, though no attempts have yet been made to parameterize the EESI-TOF response factor for different chem. species. Here, we report the first parameterization of the EESI-TOF response factor for secondary org. aerosol (SOA) at the near-mol. level based on its elemental compn. SOA was formed by ozonolysis of monoterpene or OH oxidn. of aroms. inside an oxidn. flow reactor (OFR) using ammonium nitrate as seed particles. A Vocus proton-transfer reaction mass spectrometer (Vocus-PTR) and a high-resoln. aerosol mass spectrometer (AMS) were used to det. the gas-phase mol. compn. and the particle-phase bulk chem. compn., resp. The EESI response factors towards bulk SOA coating and the inorg. seed particle core were constrained by intercomparison with the AMS. The highest bulk EESI response factor was obsd. for SOA produced from 1,3,5-trimethylbenzene, followed by those produced from d-limonene and o-cresol, consistent with previous findings. The near-mol. EESI response factors were derived from intercomparisons with VocusPTR measurements and were found to vary from 103 to 106 ion counts s-1 ppb-1, mostly within ±1 order of magnitude of their geometric mean of 104.6 ion counts s-1 ppb-1. For arom. SOA components, the EESI response factors correlated with mol. wt. and oxygen content and inversely correlated with volatility. The near-mol. response factors mostly agreed within a factor of 20 for isomers obsd. across the aroms. and biogenic systems. Parameterization of the near-mol. response factors based on the measured elemental formulas could reproduce the empirically detd. response factor for a single volatile org. compd. (VOC) system to within a factor of 5 for the configuration of our mass spectrometers. The results demonstrate that std.-free quantification using the EESI-TOF is possible.
  5. 5
    Jimenez, J. L.; Canagaratna, M. R.; Donahue, N. M.; Prevot, A. S. H.; Zhang, Q.; Kroll, J. H.; DeCarlo, P. F.; Allan, J. D.; Coe, H.; Ng, N. L. Evolution of Organic Aerosols in the Atmosphere. Science 2009, 326, 1525– 1529,  DOI: 10.1126/science.1180353
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    5
    Evolution of Organic Aerosols in the Atmosphere
    Jimenez, J. L.; Canagaratna, M. R.; Donahue, N. M.; Prevot, A. S. H.; Zhang, Q.; Kroll, J. H.; DeCarlo, P. F.; Allan, J. D.; Coe, H.; Ng, N. L.; Aiken, A. C.; Docherty, K. S.; Ulbrich, I. M.; Grieshop, A. P.; Robinson, A. L.; Duplissy, J.; Smith, J. D.; Wilson, K. R.; Lanz, V. A.; Hueglin, C.; Sun, Y. L.; Tian, J.; Laaksonen, A.; Raatikainen, T.; Rautiainen, J.; Vaattovaara, P.; Ehn, M.; Kulmala, M.; Tomlinson, J. M.; Collins, D. R.; Cubison, M. J.; Dunlea, J.; Huffman, J. A.; Onasch, T. B.; Alfarra, M. R.; Williams, P. I.; Bower, K.; Kondo, Y.; Schneider, J.; Drewnick, F.; Borrmann, S.; Weimer, S.; Demerjian, K.; Salcedo, D.; Cottrell, L.; Griffin, R.; Takami, A.; Miyoshi, T.; Hatakeyama, S.; Shimono, A.; Sun, J. Y.; Zhang, Y. M.; Dzepina, K.; Kimmel, J. R.; Sueper, D.; Jayne, J. T.; Herndon, S. C.; Trimborn, A. M.; Williams, L. R.; Wood, E. C.; Middlebrook, A. M.; Kolb, C. E.; Baltensperger, U.; Worsnop, D. R.
    Science (Washington, DC, United States) (2009), 326 (5959), 1525-1529CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
    Org. aerosol (OA) particles affect climate forcing and human health, but their sources and evolution are poorly characterized. A unifying model framework describing the atm. evolution of OA which is constrained by high time resolved measurements of its compn., volatility, and oxidn. state is presented. OA and OA precursor gases evolve by becoming increasingly oxidized, less volatile, and more hygroscopic, leading to the formation of oxygenated org. aerosols (OOA), with concns. comparable to those of SO42- aerosols throughout the Northern Hemisphere. This model framework captures the dynamic aging behavior obsd. in the atm. and lab.; it serves as a basis to improve regional and global model parameterizations.
  6. 6
    (a) Mohr, C.; Thornton, J. A.; Heitto, A.; Lopez-Hilfiker, F. D.; Lutz, A.; Riipinen, I.; Hong, J.; Donahue, N. M.; Hallquist, M.; Petäjä, T. Molecular identification of organic vapors driving atmospheric nanoparticle growth. Nat. Commun. 2019, 10, 4442,  DOI: 10.1038/s41467-019-12473-2
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    6a
    Molecular identification of organic vapors driving atmospheric nanoparticle growth
    Mohr, Claudia; Thornton, Joel A.; Heitto, Arto; Lopez-Hilfiker, Felipe D.; Lutz, Anna; Riipinen, Ilona; Hong, Juan; Donahue, Neil M.; Hallquist, Mattias; Petaejae, Tuukka; Kulmala, Markku; Yli-Juuti, Taina
    Nature Communications (2019), 10 (1), 4442CODEN: NCAOBW; ISSN:2041-1723. (Nature Research)
    Particles formed in the atm. via nucleation provide about half the no. of atm. cloud condensation nuclei, but in many locations, this process is limited by the growth of the newly formed particles. That growth is often via condensation of org. vapors. Identification of these vapors and their sources is thus fundamental for simulating changes to aerosol-cloud interactions, which are one of the most uncertain aspects of anthropogenic climate forcing. Here we present direct mol.-level observations of a distribution of org. vapors in a forested environment that can explain simultaneously obsd. atm. nanoparticle growth from 3 to 50 nm. Furthermore, the volatility distribution of these vapors is sufficient to explain nanoparticle growth without invoking particle-phase processes. The agreement between obsd. mass growth, and the growth predicted from the obsd. mass of condensing vapors in a forested environment thus represents an important step forward in the characterization of atm. particle growth.
    (b) Stolzenburg, D.; Fischer, L.; Vogel, A. L.; Heinritzi, M.; Schervish, M.; Simon, M.; Wagner, A. C.; Dada, L.; Ahonen, L. R.; Amorim, A. Rapid growth of organic aerosol nanoparticles over a wide tropospheric temperature range. Proc. Natl. Acad. Sci. U.S.A. 2018, 115, 9122– 9127,  DOI: 10.1073/pnas.1807604115
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    6b
    Rapid growth of organic aerosol nanoparticles over a wide tropospheric temperature range
    Stolzenburg, Dominik; Fischer, Lukas; Vogel, Alexander L.; Heinritzi, Martin; Schervish, Meredith; Simon, Mario; Wagner, Andrea C.; Dada, Lubna; Ahonen, Lauri R.; Amorim, Antonio; Baccarini, Andrea; Bauer, Paulus S.; Baumgartner, Bernhard; Bergen, Anton; Bianchi, Federico; Breitenlechner, Martin; Brilke, Sophia; Mazon, Stephany Buenrostro; Chen, Dexian; Dias, AntA3nio; Draper, Danielle C.; Duplissy, Jonathan; El Haddad, Imad; Finkenzeller, Henning; Frege, Carla; Fuchs, Claudia; Garmash, Olga; Gordon, Hamish; He, Xucheng; Helm, Johanna; Hofbauer, Victoria; Hoyle, Christopher R.; Kim, Changhyuk; Kirkby, Jasper; Kontkanen, Jenni; KA1/4rten, Andreas; Lampilahti, Janne; Lawler, Michael; Lehtipalo, Katrianne; Leiminger, Markus; Mai, Huajun; Mathot, Serge; Mentler, Bernhard; Molteni, Ugo; Nie, Wei; Nieminen, Tuomo; Nowak, John B.; Ojdanic, Andrea; Onnela, Antti; Passananti, Monica; PetAjA, Tuukka; J. QuAlAver, Lauriane L.; Rissanen, Matti P.; Sarnela, Nina; Schallhart, Simon; Tauber, Christian; TomA, AntA3nio; Wagner, Robert; Wang, Mingyi; Weitz, Lena; Wimmer, Daniela; Xiao, Mao; Yan, Chao; Ye, Penglin; Zha, Qiaozhi; Baltensperger, Urs; Curtius, Joachim; Dommen, Josef; Flagan, Richard C.; Kulmala, Markku; Smith, James N.; Worsnop, Douglas R.; Hansel, Armin; Donahue, Neil M.; Winkler, Paul M.
    Proceedings of the National Academy of Sciences of the United States of America (2018), 115 (37), 9122-9127CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)
    Nucleation and growth of aerosol particles from atm. vapors constitutes a major source of global cloud condensation nuclei (CCN). The fraction of newly formed particles that reaches CCN sizes is highly sensitive to particle growth rates, esp. for particle sizes <10 nm, where coagulation losses to larger aerosol particles are greatest. Recent results show that some oxidn. products from biogenic volatile org. compds. are major contributors to particle formation and initial growth. However, whether oxidized orgs. contribute to particle growth over the broad span of tropospheric temps. remains an open question, and quant. mass balance for org. growth has yet to be demonstrated at any temp. Here, in expts. performed under atm. conditions in the Cosmics Leaving Outdoor Droplets (CLOUD) chamber at the European Organization for Nuclear Research (CERN), we show that rapid growth of org. particles occurs over the range from -25°C to 25°C. The lower extent of autoxidn. at reduced temps. is compensated by the decreased volatility of all oxidized mols. This is confirmed by particle-phase compn. measurements, showing enhanced uptake of relatively less oxygenated products at cold temps. We can reproduce the measured growth rates using an aerosol growth model based entirely on the exptl. measured gas-phase spectra of oxidized org. mols. obtained from two complementary mass spectrometers. We show that the growth rates are sensitive to particle curvature, explaining widespread atm. observations that particle growth rates increase in the single-digit-nanometer size range. Our results demonstrate that org. vapors can contribute to particle growth over a wide range of tropospheric temps. from mol. cluster sizes onward.
  7. 7
    (a) Simon, M.; Dada, L.; Heinritzi, M.; Scholz, W.; Stolzenburg, D.; Fischer, L.; Wagner, A. C.; Kürten, A.; Rörup, B.; He, X. C. Molecular understanding of new-particle formation from &lt;i&amp;gt;α&lt;/i&amp;gt;-pinene between −50 and +25 °C. Atmos. Chem. Phys. 2020, 20, 9183– 9207,  DOI: 10.5194/acp-20-9183-2020
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    7a
    Molecular understanding of new-particle formation from α-pinene between -50 and +25 °C
    Simon, Mario; Dada, Lubna; Heinritzi, Martin; Scholz, Wiebke; Stolzenburg, Dominik; Fischer, Lukas; Wagner, Andrea C.; Kuerten, Andreas; Roerup, Birte; He, Xu-Cheng; Almeida, Joao; Baalbaki, Rima; Baccarini, Andrea; Bauer, Paulus S.; Beck, Lisa; Bergen, Anton; Bianchi, Federico; Braekling, Steffen; Brilke, Sophia; Caudillo, Lucia; Chen, Dexian; Chu, Biwu; Dias, Antonio; Draper, Danielle C.; Duplissy, Jonathan; El-Haddad, Imad; Finkenzeller, Henning; Frege, Carla; Gonzalez-Carracedo, Loic; Gordon, Hamish; Granzin, Manuel; Hakala, Jani; Hofbauer, Victoria; Hoyle, Christopher R.; Kim, Changhyuk; Kong, Weimeng; Lamkaddam, Houssni; Lee, Chuan P.; Lehtipalo, Katrianne; Leiminger, Markus; Mai, Huajun; Manninen, Hanna E.; Marie, Guillaume; Marten, Ruby; Mentler, Bernhard; Molteni, Ugo; Nichman, Leonid; Nie, Wei; Ojdanic, Andrea; Onnela, Antti; Partoll, Eva; Petaejae, Tuukka; Pfeifer, Joschka; Philippov, Maxim; Quelever, Lauriane L. J.; Ranjithkumar, Ananth; Rissanen, Matti P.; Schallhart, Simon; Schobesberger, Siegfried; Schuchmann, Simone; Shen, Jiali; Sipilae, Mikko; Steiner, Gerhard; Stozhkov, Yuri; Tauber, Christian; Tham, Yee J.; Tome, Antonio R.; Vazquez-Pufleau, Miguel; Vogel, Alexander L.; Wagner, Robert; Wang, Mingyi; Wang, Dongyu S.; Wang, Yonghong; Weber, Stefan K.; Wu, Yusheng; Xiao, Mao; Yan, Chao; Ye, Penglin; Ye, Qing; Zauner-Wieczorek, Marcel; Zhou, Xueqin; Baltensperger, Urs; Dommen, Josef; Flagan, Richard C.; Hansel, Armin; Kulmala, Markku; Volkamer, Rainer; Winkler, Paul M.; Worsnop, Douglas R.; Donahue, Neil M.; Kirkby, Jasper; Curtius, Joachim
    Atmospheric Chemistry and Physics (2020), 20 (15), 9183-9207CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
    Highly oxygenated org. mols. (HOMs) contribute substantially to the formation and growth of atm. aerosol particles, which affect air quality, human health and Earth's climate. HOMs are formed by rapid, gas-phase autoxidn. of volatile org. compds. (VOCs) such as α-pinene, the most abundant monoterpene in the atm. Due to their abundance and low volatility, HOMs can play an important role in new-particle formation (NPF) and the early growth of atm. aerosols, even without any further assistance of other low-volatility compds. such as sulfuric acid. Both the autoxidn. reaction forming HOMs and their NPF rates are expected to be strongly dependent on temp. However, exptl. data on both effects are limited. Dedicated expts. were performed at the CLOUD (Cosmics Leaving OUtdoor Droplets) chamber at CERN to address this question. In this study, we show that a decrease in temp. (from +25 to -50 °C) results in a reduced HOM yield and reduced oxidn. state of the products, whereas the NPF rates (J1.7 nm) increase substantially. Measurements with two different chem. ionization mass spectrometers (using nitrate and protonated water as reagent ion, resp.) provide the mol. compn. of the gaseous oxidn. products, and a two-dimensional volatility basis set (2D VBS) model provides their volatility distribution. The HOM yield decreases with temp. from 6.2 % at 25 °C to 0.7 % at -50 °C. However, there is a strong redn. of the satn. vapor pressure of each oxidn. state as the temp. is reduced. Overall, the redn. in volatility with temp. leads to an increase in the nucleation rates by up to 3 orders of magnitude at -50 °C compared with 25 °C. In addn., the enhancement of the nucleation rates by ions decreases with decreasing temp., since the neutral mol. clusters have increased stability against evapn. The resulting data quantify how the interplay between the temp.-dependent oxidn. pathways and the assocd. vapor pressures affect biogenic NPF at the mol. level. Our measurements, therefore, improve our understanding of pure biogenic NPF for a wide range of tropospheric temps. and precursor concns.
    (b) Heinritzi, M.; Dada, L.; Simon, M.; Stolzenburg, D.; Wagner, A. C.; Fischer, L.; Ahonen, L. R.; Amanatidis, S.; Baalbaki, R.; Baccarini, A. Molecular understanding of the suppression of new-particle formation by isoprene. Atmos. Chem. Phys. 2020, 20, 11809– 11821,  DOI: 10.5194/acp-20-11809-2020
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    7b
    Molecular understanding of the suppression of new-particle formation by isoprene
    Heinritzi, Martin; Dada, Lubna; Simon, Mario; Stolzenburg, Dominik; Wagner, Andrea C.; Fischer, Lukas; Ahonen, Lauri R.; Amanatidis, Stavros; Baalbaki, Rima; Baccarini, Andrea; Bauer, Paulus S.; Baumgartner, Bernhard; Bianchi, Federico; Brilke, Sophia; Chen, Dexian; Chiu, Randall; Dias, Antonio; Dommen, Josef; Duplissy, Jonathan; Finkenzeller, Henning; Frege, Carla; Fuchs, Claudia; Garmash, Olga; Gordon, Hamish; Granzin, Manuel; El Haddad, Imad; He, Xucheng; Helm, Johanna; Hofbauer, Victoria; Hoyle, Christopher R.; Kangasluoma, Juha; Keber, Timo; Kim, Changhyuk; Kuerten, Andreas; Lamkaddam, Houssni; Laurila, Tiia M.; Lampilahti, Janne; Lee, Chuan Ping; Lehtipalo, Katrianne; Leiminger, Markus; Mai, Huajun; Makhmutov, Vladimir; Manninen, Hanna Elina; Marten, Ruby; Mathot, Serge; Mauldin, Roy Lee; Mentler, Bernhard; Molteni, Ugo; Mueller, Tatjana; Nie, Wei; Nieminen, Tuomo; Onnela, Antti; Partol, Eva; Passananti, Monica; Petaejae, Tuukka; Pfeifer, Joschka; Pospisilova, Veronika; Quelever, Lauriane L. J.; Rissanen, Matti P.; Rose, Clemence; Schobesberger, Siegfried; Scholz, Wiebke; Scholze, Kay; Sipilae, Mikko; Steiner, Gerhard; Stozhkov, Yuri; Tauber, Christian; Tham, Yee Jun; Vazquez-Pufleau, Miguel; Virtanen, Annele; Vogel, Alexander L.; Volkamer, Rainer; Wagner, Robert; Wang, Mingyi; Weitz, Lena; Wimmer, Daniela; Xiao, Mao; Yan, Chao; Ye, Penglin; Zha, Qiaozhi; Zhou, Xueqin; Amorim, Antonio; Baltensperger, Urs; Hanse, Armin; Kulmala, Markku; Tome, Antonio; Winkler, Paul M.; Worsnop, Douglas R.; Donahue, Neil M.; Kirkby, Jasper; Curtius, Joachim
    Atmospheric Chemistry and Physics (2020), 20 (20), 11809-11821CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
    Nucleation of atm. vapors produces more than half of global cloud condensation nuclei and so has an important influence on climate. Recent studies show that monoterpene (C10H16) oxidn. yields highly oxygenated products that can nucleate with or without sulfuric acid. Monoterpenes are emitted mainly by trees, frequently together with isoprene (C5H8), which has the highest global emission of all org. vapors. Previous studies have shown that isoprene suppresses new-particle formation from monoterpenes, but the cause of this suppression is under debate. Here, in expts. performed under atm. conditions in the CERN CLOUD chamber, we show that isoprene reduces the yield of highly oxygenated dimers with 19 or 20 carbon atoms which drive particle nucleation and early growth while increasing the prodn. of dimers with 14 or 15 carbon atoms. The dimers (termed C20 and C15, resp.) are produced by termination reactions between pairs of peroxy radicals (RO2·) arising from monoterpenes or isoprene. Compared with pure monoterpene conditions, isoprene reduces nucleation rates at 1.7 nm (depending on the isoprene / monoterpene ratio) and approx. halves particle growth rates between 1.3 and 3.2 nm. However, above 3.2 nm, C15 dimers contribute to secondary org. aerosol, and the growth rates are unaffected by isoprene. We further show that increased hydroxyl radical (OH·) reduces particle formation in our chem. system rather than enhances it as previously proposed, since it increases isoprene-derived RO2· radicals that reduce C20 formation. RO2· termination emerges as the crit. step that dets. the highly oxygenated org. mol. (HOM) distribution and the corresponding nucleation capability. Species that reduce the C20 yield, such as NO, HO2 and as we show isoprene, can thus effectively reduce biogenic nucleation and early growth. Therefore the formation rate of org. aerosol in a particular region of the atm. under study will vary according to the precise ambient conditions.
    (c) Ye, Q.; Wang, M.; Hofbauer, V.; Stolzenburg, D.; Chen, D.; Schervish, M.; Vogel, A.; Mauldin, R. L.; Baalbaki, R.; Brilke, S. Molecular Composition and Volatility of Nucleated Particles from α-Pinene Oxidation between −50 °C and +25 °C. Environ. Sci. Technol. 2019, 53, 12357– 12365,  DOI: 10.1021/acs.est.9b03265
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    7c
    Molecular Composition and Volatility of Nucleated Particles from α-Pinene Oxidation between -50 °C and +25 °C
    Ye, Qing; Wang, Mingyi; Hofbauer, Victoria; Stolzenburg, Dominik; Chen, Dexian; Schervish, Meredith; Vogel, Alexander; Mauldin, Roy L.; Baalbaki, Rima; Brilke, Sophia; Dada, Lubna; Dias, Antonio; Duplissy, Jonathan; El Haddad, Imad; Finkenzeller, Henning; Fischer, Lukas; He, Xucheng; Kim, Changhyuk; Kurten, Andreas; Lamkaddam, Houssni; Lee, Chuan Ping; Lehtipalo, Katrianne; Leiminger, Markus; Manninen, Hanna E.; Marten, Ruby; Mentler, Bernhard; Partoll, Eva; Petaja, Tuukka; Rissanen, Matti; Schobesberger, Siegfried; Schuchmann, Simone; Simon, Mario; Tham, Yee Jun; Vazquez-Pufleau, Miguel; Wagner, Andrea C.; Wang, Yonghong; Wu, Yusheng; Xiao, Mao; Baltensperger, Urs; Curtius, Joachim; Flagan, Richard; Kirkby, Jasper; Kulmala, Markku; Volkamer, Rainer; Winkler, Paul M.; Worsnop, Douglas; Donahue, Neil M.
    Environmental Science & Technology (2019), 53 (21), 12357-12365CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    We use a real-time temp.-programmed desorption chem.-ionization mass spectrometer (FIGAERO-CIMS) to measure particle-phase compn. and volatility of nucleated particles, studying pure α-pinene oxidn. over a wide temp. range (-50° to +25°) in the CLOUD chamber at CERN. Highly-oxygenated org. mols. are much more abundant in particles formed at higher temps., shifting the compds. towards higher O:C and lower intrinsic (300 K) volatility. We find that pure biogenic nucleation and growth depends only weakly on temp. This is because the pos. temp. dependence of degree of oxidn. (and polarity) and the neg. temp. dependence of volatility counteract each other. Unlike prior work that relied on estd. volatility, we directly measure volatility via calibrated temp. programmed desorption. The particle-phase measurements are consistent with gas-phase results and indicate that during new-particle formation from α-pinene oxidn., gas-phase chem. directly dets. the properties of materials in the condensed phase. We now have consistency between measured gas-phase product concns., product volatility, measured and modeled growth rates, and the particle compn. over most temps. found in the troposphere.
    (d) Frege, C.; Ortega, I. K.; Rissanen, M. P.; Praplan, A. P.; Steiner, G.; Heinritzi, M.; Ahonen, L.; Amorim, A.; Bernhammer, A.-K.; Bianchi, F. Influence of temperature on the molecular composition of ions and charged clusters during pure biogenic nucleation. Atmos. Chem. Phys. 2018, 18, 65– 79,  DOI: 10.5194/acp-18-65-2018
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    7d
    Influence of temperature on the molecular composition of ions and charged clusters during pure biogenic nucleation
    Frege, Carla; Ortega, Ismael K.; Rissanen, Matti P.; Praplan, Arnaud P.; Steiner, Gerhard; Heinritzi, Martin; Ahonen, Lauri; Amorim, Antonio; Bernhammer, Anne-Kathrin; Bianchi, Federico; Brilke, Sophia; Breitenlechner, Martin; Dada, Lubna; Dias, Antonio; Duplissy, Jonathan; Ehrhart, Sebastian; El-Haddad, Imad; Fischer, Lukas; Fuchs, Claudia; Garmash, Olga; Gonin, Marc; Hansel, Armin; Hoyle, Christopher R.; Jokinen, Tuija; Junninen, Heikki; Kirkby, Jasper; Kurten, Andreas; Lehtipalo, Katrianne; Leiminger, Markus; Mauldin, Roy Lee; Molteni, Ugo; Nichman, Leonid; Petaja, Tuukka; Sarnela, Nina; Schobesberger, Siegfried; Simon, Mario; Sipila, Mikko; Stolzenburg, Dominik; Tome, Antonio; Vogel, Alexander L.; Wagner, Andrea C.; Wagner, Robert; Xiao, Mao; Yan, Chao; Ye, Penglin; Curtius, Joachim; Donahue, Neil M.; Flagan, Richard C.; Kulmala, Markku; Worsnop, Douglas R.; Winkler, Paul M.; Dommen, Josef; Baltensperger, Urs
    Atmospheric Chemistry and Physics (2018), 18 (1), 65-79CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
    It was recently shown by the CERN CLOUD expt. that biogenic highly oxygenated mols. (HOMs) form particles under atm. conditions in the absence of sulfuric acid, where ions enhance the nucleation rate by 1-2 orders of magnitude. The biogenic HOMs were produced from ozonolysis of α-pinene at 5 °C. Here, we extend this study to compare the mol. compn. of pos. and neg. HOM clusters measured with atm. pressure interface time-of-flight mass spectrometers (APi-TOFs), at three different temps. (25, 5 and -25 °C). Most neg. HOM clusters include a nitrate (NO3- ) ion, and the spectra are similar to those seen in the nighttime boreal forest. On the other hand, most pos. HOM clusters include an ammonium (NH4+) ion, and the spectra are characterized by mass bands that differ in their mol. wt. by ∼20 C atoms, corresponding to HOM dimers. At lower temps. the av. oxygen to carbon (O : C) ratio of the HOM clusters decreases for both polarities, reflecting an overall redn. of HOM formation with decreasing temp. This indicates a decrease in the rate of autoxidn. with temp. due to a rather high activation energy as has previously been detd. by quantum chem. calcns. Furthermore, at the lowest temp. (∼25 °C), the presence of C30 clusters shows that HOM monomers start to contribute to the nucleation of pos. clusters. These exptl. findings are supported by quantum chem. calcns. of the binding energies of representative neutral and charged clusters.
    (e) Lehtipalo, K.; Yan, C.; Dada, L.; Bianchi, F.; Xiao, M.; Wagner, R.; Stolzenburg, D.; Ahonen, L. R.; Amorim, A.; Baccarini, A. Multicomponent new particle formation from sulfuric acid, ammonia, and biogenic vapors. Sci. Adv. 2018, 4, eaau5363  DOI: 10.1126/sciadv.aau5363
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  8. 8
    (a) Dommen, J.; Metzger, A.; Duplissy, J.; Kalberer, M.; Alfarra, M. R.; Gascho, A.; Weingartner, E.; Prevot, A. S. H.; Verheggen, B.; Baltensperger, U. Laboratory observation of oligomers in the aerosol from isoprene/NOx photooxidation. Geophys. Res. Lett. 2006, 33, L13805,  DOI: 10.1029/2006gl026523
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    8a
    Laboratory observation of oligomers in the aerosol from isoprene/NOx photooxidation
    Dommen, J.; Metzger, A.; Duplissy, J.; Kalberer, M.; Alfarra, M. R.; Gascho, A.; Weingartner, E.; Prevot, A. S. H.; Verheggen, B.; Baltensperger, U.
    Geophysical Research Letters (2006), 33 (13), L13805/1-L13805/5CODEN: GPRLAJ; ISSN:0094-8276. (American Geophysical Union)
    Compds. assigned to be oxidn. products of isoprene (2-methyl-1,3-butadiene) have recently been obsd. in ambient aerosols, suggesting that isoprene might play an important role in secondary org. aerosol (SOA) formation due to its large global source strength. SOA yields from photooxidn. of isoprene and NOx in a chamber agree fairly well with previous data. Matrix assisted laser desorption/ionization mass spectrometry showed the formation of high mol. wt. compds. over the course of 15-h expts. Concurrently, the volatility of the SOA decreased markedly as obsd. by a tandem differential mobility analyzer. The vol. fraction remaining of SOA at 150°C increased steadily from 5 to 25% during the same expts. These observations are attributed to oligomerization reactions occurring in the aerosol phase. Under dry conditions a lower volatility was obsd.
    (b) Kalberer, M.; Paulsen, D.; Sax, M.; Steinbacher, M.; Dommen, J.; Prevot, A. S. H.; Fisseha, R.; Weingartner, E.; Frankevich, V.; Zenobi, R. Identification of Polymers as Major Components of Atmospheric Organic Aerosols. Science 2004, 303, 1659– 1662,  DOI: 10.1126/science.1092185
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    8b
    Identification of Polymers as Major Components of Atmospheric Organic Aerosols
    Kalberer, M.; Paulsen, D.; Sax, M.; Steinbacher, M.; Dommen, J.; Prevot, A. S. H.; Fisseha, R.; Weingartner, E.; Frankevich, V.; Zenobi, R.; Baltensperger, U.
    Science (Washington, DC, United States) (2004), 303 (5664), 1659-1662CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
    The results from photooxidn. of arom. compds. in a reaction chamber show that a substantial fraction of the org. aerosol mass is composed of polymers. This polymn. results from reactions of carbonyls and their hydrates. After aging for more than 20 h, about 50% of the particle mass consists of polymers with a mol. mass up to 1000 daltons. This results in a lower volatility of this secondary org. aerosol and a higher aerosol yield than a model using vapor pressures of individual org. species would predict.
    (c) Laskin, A.; Laskin, J.; Nizkorodov, S. A. Mass spectrometric approaches for chemical characterisation of atmospheric aerosols: critical review of the most recent advances. Environ. Chem. 2012, 9, 163– 189,  DOI: 10.1071/en12052
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    8c
    Mass spectrometric approaches for chemical characterisation of atmospheric aerosols: critical review of the most recent advances
    Laskin, Alexander; Laskin, Julia; Nizkorodov, Sergey A.
    Environmental Chemistry (2012), 9 (3), 163-189CODEN: ECNHAA; ISSN:1449-8979. (CSIRO Publishing)
    A review. Environmental contextAtmospheric aerosols have profound effects on the environment through several physicochem. processes, such as absorption and scattering of sunlight, heterogeneous gas-particle reactions and adverse effects on the respiratory and cardiovascular systems. Understanding aerosol atm. chem. and its environmental impact requires comprehensive characterization of the phys. and chem. properties of particles. Results from mass spectrometry provide important new insights into the origin of atm. aerosols, the evolution of their physicochem. properties, their reactivity and their effect on the environment. This manuscript presents an overview of the most recent instrument developments for the field and lab. applications of mass spectrometry (MS) to investigate the chem. and physics of atm. aerosols. A range of MS instruments, employing different sample introduction methods, ionisation and mass detection techniques are used both for online' and offline' characterization of aerosols. Online MS techniques enable detection of individual particles with simultaneous measurement of particle size distributions and aerodynamic characteristics and are ideally suited for field studies that require high temporal resoln. Offline MS techniques provide a means for detailed mol.-level anal. of aerosol samples, which is essential to gain fundamental knowledge regarding aerosol chem., mechanisms of particle formation and atm. aging. Combined, complementary MS techniques provide comprehensive information on the chem. compn., size, morphol. and phase of aerosols - data of key importance for evaluating hygroscopic and optical properties of particles, their health effects, understanding their origins and atm. evolution. Over the last few years, developments and applications of MS techniques in aerosol research have expanded remarkably as evident by skyrocketing publication statistics. The goal of this review is to present the most recent developments in the field of aerosol mass spectrometry for the time period of late 2010 to early 2012, which have not been conveyed in previous reviews.
    (d) Walser, M. L.; Desyaterik, Y.; Laskin, J.; Laskin, A.; Nizkorodov, S. A. High-resolution mass spectrometric analysis of secondary organic aerosol produced by ozonation of limonene. Phys. Chem. Chem. Phys. 2008, 10, 1009– 1022,  DOI: 10.1039/B712620D
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    8d
    High-resolution mass spectrometric analysis of secondary organic aerosol produced by ozonation of limonene
    Walser, Maggie L.; Desyaterik, Yury; Laskin, Julia; Laskin, Alexander; Nizkorodov, Sergey A.
    Physical Chemistry Chemical Physics (2008), 10 (7), 1009-1022CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
    The chem. compn. of secondary org. aerosols (SOA) formed from O3-initiated oxidn. of limonene was characterized by high-resoln. electro-spray ionization/mass spectrometry in pos. and neg. ion modes. Mass spectra showed a large no. of monomeric (m/z <300) and oligomeric (m/z >300) condensed oxidn. products. A combination of high resolving power (m/Δm ∼60,000) and Kendrick mass defect anal. made it possible to unambiguously det. the mol. compn. of hundreds of individual compds. in SOA samples. Van Krevelen anal. showed SOA compds. were heavily oxidized, with av. O:C ratios of 0.43 and 0.50 detd. from pos. and neg. ion mode spectra, resp. A possible reaction mechanism for formation of first generation SOA mol. components is presented. This mechanism includes known isomerization and addn. reactions of carbonyl oxide intermediates generated during limonene ozonation. Also, it includes isomerization and decompn. pathways for alkoxy radicals resulting from unimol. decompn. of carbonyl oxides which were disregarded in previous studies. Isomerization reactions yielded numerous products with a progressively increasing no. of alc. and carbonyl groups; C-C bond scission reactions in alkoxy radicals shortened the C chain. Together these reactions yielded a large no. of isomeric products with broadly distributed masses. A qual. agreement was obsd. between the no. and degree of oxidn. of predicted and measured reaction products in the monomer product range.
    (e) Bateman, A. P.; Walser, M. L.; Desyaterik, Y.; Laskin, J.; Laskin, A.; Nizkorodov, S. A. The Effect of Solvent on the Analysis of Secondary Organic Aerosol Using Electrospray Ionization Mass Spectrometry. Environ. Sci. Technol. 2008, 42, 7341– 7346,  DOI: 10.1021/es801226w
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    8e
    The Effect of Solvent on the Analysis of Secondary Organic Aerosol Using Electrospray Ionization Mass Spectrometry
    Bateman, Adam P.; Walser, Maggie L.; Desyaterik, Yury; Laskin, Julia; Laskin, Alexander; Nizkorodov, Sergey A.
    Environmental Science & Technology (2008), 42 (19), 7341-7346CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    This work examd. the effect of solvent on org. aerosol ext. anal. by electro-spray ionization/mass spectrometry (ESI/MS). Secondary org. aerosol (SOA) produced by ozonation of d-limonene and several org. mols. with functional groups typical for OA constituents, were extd. in methanol, d3-methanol, acetonitrile, and d3-acetonitrile to assess the extent and relative rates of reactions between analyte and solvent. High resoln. ESI-MS showed reactions of carbonyls with methanol produced significant amts. of hemiacetals and acetals on time scales of several minutes to several days; reaction rates increased in acidified soln. Carboxylic acid groups reacted with methanol forming esters. Acetonitrile exts. demonstrated no evidence of reactions with analyte mols., suggesting acetonitrile is the preferred solvent for SOA extn. Using solvent-analyte reactivity as a tool to improve characterization of functional groups in complex org. mixts. was demonstrated. Direct comparison between mass spectra of the same SOA samples extd. in methanol vs. acetonitrile estd. lower limits for relative fractions of carbonyls (≥42%) and carboxylic acids (≥55%) in d-limonene SOA.
  9. 9
    (a) Müller, M.; Piel, F.; Gutmann, R.; Sulzer, P.; Hartungen, E.; Wisthaler, A. A novel method for producing NH4+ reagent ions in the hollow cathode glow discharge ion source of PTR-MS instruments. Int. J. Mass Spectrom. 2020, 447, 116254,  DOI: 10.1016/j.ijms.2019.116254
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    9a
    A novel method for producing NH+4 reagent ions in the hollow cathode glow discharge ion source of PTR-MS instruments
    Mueller, Markus; Piel, Felix; Gutmann, Rene; Sulzer, Philipp; Hartungen, Eugen; Wisthaler, Armin
    International Journal of Mass Spectrometry (2020), 447 (), 116254CODEN: IMSPF8; ISSN:1387-3806. (Elsevier B.V.)
    Proton-transfer-reaction mass spectrometry (PTR-MS) is seeing an increased use of NH+4 ions for the detection of amines and labile oxygenated org. compds. NH+4 ions are usually generated from ammonia or ammonium-contg. chems. We herein present a simple method for generating NH+4 reagent ions in the hollow cathode glow discharge ion source that nowadays most proton-transfer-reaction mass spectrometry (PTR-MS) instruments are equipped with. We show that NH+4 ions can be generated in high purity and yield by simply introducing a mixt. of water vapor and nitrogen in the ion source. We also show that rapid switching (~ 10 s loss of data) between the H3O+ and NH+4 operation modes is possible. Our new method can be easily implemented in most PTR-MS instruments that are currently in use, thus opening the possibility to easily operate the PTR-MS analyzer in the NH+4 chem. ionization mode.
    (b) Leglise, J.; Müller, M.; Piel, F.; Otto, T.; Wisthaler, A. Bulk Organic Aerosol Analysis by Proton-Transfer-Reaction Mass Spectrometry: An Improved Methodology for the Determination of Total Organic Mass, O:C and H:C Elemental Ratios, and the Average Molecular Formula. Anal. Chem. 2019, 91, 12619– 12624,  DOI: 10.1021/acs.analchem.9b02949
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    9b
    Bulk Organic Aerosol Analysis by Proton-Transfer-Reaction Mass Spectrometry: An Improved Methodology for the Determination of Total Organic Mass, O:C and H:C Elemental Ratios, and the Average Molecular Formula
    Leglise, Joris; Muller, Markus; Piel, Felix; Otto, Tobias; Wisthaler, Armin
    Analytical Chemistry (Washington, DC, United States) (2019), 91 (20), 12619-12624CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)
    The authors recently showed (M. Muller, et al., 2017) how a proton-transfer-reaction mass spectrometry (PTR-MS) analyzer measured particulate org. matter in urban atmospheres using a chem. anal. of aerosol online (CHARON) inlet. Initial CHARON studies did not account for fragmentation of protonated analyte mols., which introduced a small but significant neg. bias in bulk org. aerosol parameters detn. This work examd. the ionic fragmentation of 26 oxidized org. compds. typically occurring in atm. particles. This allowed the authors to derive a correction algorithm to det. the bulk org. mass concn. (mOA), the bulk-av. H:C ratio ([H:C]bulk), the bulk-av. O:C ratio ([O:C]bulk), and the bulk-av. mol. formula, MFbulk. The correction algorithm was validated against AMS data using two sets of published data. The authors then detd. MFbulk of particles generated from an α-pinene/O3 reaction, and compared and discussed results in relation to the literature.
    (c) Eichler, P.; Müller, M.; D’Anna, B.; Wisthaler, A. A novel inlet system for online chemical analysis of semi-volatile submicron particulate matter. Atmos. Meas. Tech. 2015, 8, 1353– 1360,  DOI: 10.5194/amt-8-1353-2015
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    9c
    A novel inlet system for online chemical analysis of semi-volatile submicron particulate matter
    Eichler, P.; Mueller, M.; D'Anna, B.; Wisthaler, A.
    Atmospheric Measurement Techniques (2015), 8 (3), 1353-1360CODEN: AMTTC2; ISSN:1867-8548. (Copernicus Publications)
    We herein present a novel modular inlet system designed to be coupled to low-pressure gas analyzers for online chem. characterization of semi-volatile submicron particles. The "chem. anal. of aerosol online" (CHARON) inlet consists of a gas-phase denuder for stripping off gasphase analytes, an aerodynamic lens for particle collimation combined with an inertial sampler for the particle-enriched flow and a thermodesorption unit for particle volatilization prior to chem. anal. The denuder was measured to remove gas-phase orgs. with an efficiency > 99.999% and to transmit particles in the 100-750 nm size range with a 75-90% efficiency. The measured av. particle enrichment factor in the subsampling flow from the aerodynamic lens was 25.6, which is a factor of 3 lower than the calcd. theor. optimum. We coupled the CHARON inlet to a proton-transferreaction time-of-flight mass spectrometer (PTR-ToF-MS) which quant. detects most org. analytes and ammonia. The combined CHARON-PTR-ToF-MS setup is thus capable of measuring both the org. and the ammonium fraction in submicron particles in real time. Individual org. compds. can be detected down to levels of 10-20 ngm-3 Two proof-of-principle studies were carried out for demonstrating the anal. power of this new instrumental setup: (i) oxygenated orgs. and their partitioning between the gas and the particulate phase were obsd. from the reaction of limonene with ozone and (ii) nicotine was measured in cigarette smoke particles demonstrating that selected org. target compds. can be detected in submicron particles in real time.
    (d) Huang, W.; Saathoff, H.; Shen, X.; Ramisetty, R.; Leisner, T.; Mohr, C. Chemical Characterization of Highly Functionalized Organonitrates Contributing to Night-Time Organic Aerosol Mass Loadings and Particle Growth. Environ. Sci. Technol. 2019, 53, 1165– 1174,  DOI: 10.1021/acs.est.8b05826
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    9d
    Chemical Characterization of Highly Functionalized Organonitrates Contributing to Night-Time Organic Aerosol Mass Loadings and Particle Growth
    Huang, Wei; Saathoff, Harald; Shen, Xiaoli; Ramisetty, Ramakrishna; Leisner, Thomas; Mohr, Claudia
    Environmental Science & Technology (2019), 53 (3), 1165-1174CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    Reactions of volatile org. compds. (VOC) with NO3 radicals and of reactive intermediates of oxidized VOC with NOx can lead to the formation of highly functionalized organonitrates (ON). We present quant. and chem. information on ON contributing to high night-time org. aerosol (OA) mass concns. measured during July-August 2016 in a rural area in southwest Germany. A filter inlet for gases and aerosols coupled to a high-resoln. time-of-flight chem. ionization mass spectrometer (FIGAERO-HR-ToF-CIMS) was used to analyze the mol. compn. of ON in both the gas and particle phase. We find larger contributions of ON to OA mass during the night. Identified ON are highly functionalized, with 4 to 12 oxygen atoms. The diel patterns of ON compds. with 5, 7, 10, or 15 carbon atoms per mol. vary, indicating a corresponding behavior of their potential precursor VOC. The temporal behavior of ON after sunset correlates with that of the no. concn. of ultrafine particles, indicating a potential role of ON in night-time new particle formation (NPF) regularly obsd. at this location. We est. an ON contribution of 18-25% to the mass increase of newly formed particles after sunset. Our study provides insights into the chem. compn. of highly functionalized ON in the rural atm. and the role of anthropogenic emissions for night-time SOA formation in an area where biogenic VOC emissions dominate.
    (e) Mohr, C.; Lopez-Hilfiker, F. D.; Yli-Juuti, T.; Heitto, A.; Lutz, A.; Hallquist, M.; D’Ambro, E. L.; Rissanen, M. P.; Hao, L.; Schobesberger, S. Ambient observations of dimers from terpene oxidation in the gas phase: Implications for new particle formation and growth. Geophys. Res. Lett. 2017, 44, 2958– 2966,  DOI: 10.1002/2017gl072718
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    9e
    Ambient observations of dimers from terpene oxidation in the gas phase: Implications for new particle formation and growth
    Mohr, Claudia; Lopez-Hilfiker, Felipe D.; Yli-Juuti, Taina; Heitto, Arto; Lutz, Anna; Hallquist, Mattias; D'Ambro, Emma L.; Rissanen, Matti P.; Hao, Liqing; Schobesberger, Siegfried; Kulmala, Markku; Mauldin, Roy L., III; Makkonen, Ulla; Sipilae, Mikko; Petaejae, Tuukka; Thornton, Joel A.
    Geophysical Research Letters (2017), 44 (6), 2958-2966CODEN: GPRLAJ; ISSN:1944-8007. (Wiley-Blackwell)
    We present ambient observations of dimeric monoterpene oxidn. products (C16-20HyO6-9) in gas and particle phases in the boreal forest in Finland in spring 2013 and 2014, detected with a chem. ionization mass spectrometer with a filter inlet for gases and aerosols employing acetate and iodide as reagent ions. These are among the first online dual-phase observations of such dimers in the atm. Estd. satn. concns. of 10-15 to 10-6 μg m-3 (based on obsd. thermal desorptions and group-contribution methods) and measured gas-phase concns. of 10-3 to 10-2 μg m-3 (∼106-107 mols. cm-3) corroborate a gas-phase formation mechanism. Regular new particle formation (NPF) events allowed insights into the potential role dimers may play for atm. NPF and growth. The observationally constrained Model for Acid-Base chem. in NAnoparticle Growth indicates a contribution of ∼5% to early stage particle growth from the ∼60 gaseous dimer compds.
  10. 10
    Wu, C.; Bell, D. M.; Graham, E. L.; Haslett, S.; Riipinen, I.; Baltensperger, U.; Bertrand, A.; Giannoukos, S.; Schoonbaert, J.; El Haddad, I. Photolytically induced changes in composition and volatility of biogenic secondary organic aerosol from nitrate radical oxidation during night-to-day transition. Atmos. Chem. Phys. 2021, 21, 14907– 14925,  DOI: 10.5194/acp-21-14907-2021
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    10
    Photolytically induced changes in composition and volatility of biogenic secondary organic aerosol from nitrate radical oxidation during night-to-day transition
    Wu, Cheng; Bell, David M.; Graham, Emelie L.; Haslett, Sophie; Riipinen, Ilona; Baltensperger, Urs; Bertrand, Amelie; Giannoukos, Stamatios; Schoonbaert, Janne; El Haddad, Imad; Prevot, Andre S. H.; Huang, Wei; Mohr, Claudia
    Atmospheric Chemistry and Physics (2021), 21 (19), 14907-14925CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
    Night-time reactions of biogenic volatile org. compds. (BVOCs) and nitrate radicals (NO3) can lead to the formation of NO3-initiated biogenic secondary org. aerosol (BSOANO3). Here, we study the impacts of light exposure on the chem. compn. and volatility of BSOANO3 formed in the dark from three precursors (isoprene, α-pinene, and β-caryophyllene) in atm. simulation chamber expts. Our study represents BSOANO3 formation conditions where reactions between peroxy radicals (RO2 + RO2) and between RO2 and NO3 are favored. The emphasis here is on the identification of particle-phase organonitrates (ONs) formed in the dark and their changes during photolytic ageing on timescales of ~ 1 h. The chem. compn. of particle-phase compds. was measured with a chem. ionization mass spectrometer with a filter inlet for gases and aerosols (FIGAERO-CIMS) and an extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF). Volatility information on BSOANO3 was derived from FIGAERO-CIMS desorption profiles (thermograms) and a volatility tandem differential mobility analyzer (VTDMA). During photolytic ageing, there was a relatively small change in mass due to evapn. (< 5% for the isoprene and α-pinene BSOANO3, and 12% for the β-caryophyllene BSOANO3), but we obsd. significant changes in the chem. compn. of the BSOANO3. Overall, 48%, 44%, and 60% of the resp. total signal for the isoprene, α-pinene, and β-caryophyllene BSOANO3 was sensitive to photolytic ageing and exhibited decay. The photolabile compds. include both monomers and oligomers. Oligomers can decomp. into their monomer units through photolysis of the bonds (e.g. likely O-O) between them. Fragmentation of both oligomers and monomers also happened at other positions, causing the formation of compds. with shorter carbon skeletons. The cleavage of the nitrate functional group from the carbon chain was likely not a main degrdn. pathway in our expts. In addn., photolytic degrdn. of compds. changes their volatility and can lead to evapn. We use different methods to assess bulk volatilities and discuss their changes during both dark ageing and photolysis in the context of the chem. changes that we obsd. We also reveal large uncertainties in satn. vapor pressure estd. from parameterizations for the ON oligomers with multiple nitrate groups. Overall, our results suggest that photolysis causes photodegrdn. of a substantial fraction of BSOANO3, changes both the chem. compn. and the bulk volatility of the particles, and might be a potentially important loss pathway of BSOANO3 during the night-to-day transition.
  11. 11
    Lopez-Hilfiker, F. D.; Pospisilova, V.; Huang, W.; Kalberer, M.; Mohr, C.; Stefenelli, G.; Thornton, J. A.; Baltensperger, U.; Prevot, A. S. H.; Slowik, J. G. An extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF) for online measurement of atmospheric aerosol particles. Atmos. Meas. Tech. 2019, 12, 4867– 4886,  DOI: 10.5194/amt-12-4867-2019
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    11
    An extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF) for online measurement of atmospheric aerosol particles
    Lopez-Hilfiker, Felipe D.; Pospisilova, Veronika; Huang, Wei; Kalberer, Markus; Mohr, Claudia; Stefenelli, Giulia; Thornton, Joel A.; Baltensperger, Urs; Prevot, Andre S. H.; Slowik, Jay G.
    Atmospheric Measurement Techniques (2019), 12 (9), 4867-4886CODEN: AMTTC2; ISSN:1867-8548. (Copernicus Publications)
    Real-time, online measurements of atm. org. aerosol (OA) compn. are an essential tool for detg. the emissions sources and physicochem. processes governing aerosol effects on climate and health. Aerosol particles are continuously sampled into the EESI-TOF, where they intersect a spray of charged droplets generated by a conventional electrospray probe. Sol. components are extd. and then ionized as the droplets are evapd. The EESI-TOF achieves a linear response to mass, with detection limits on the order of 1 to 10 ng m-3 in 5 s for typical atmospherically relevant compds. In contrast to conventional electrospray systems, the EESI-TOF response is not significantly affected by a changing OA matrix for the systems investigated. Although the relative sensitivities to a variety of com. available org. stds. vary by more than a factor of 30, the bulk sensitivity to secondary org. aerosol generated from individual precursor gases varies by only a factor of 15. Further, the ratio of compd.-by-compd. sensitivities between the EESI-TOF and an iodide adduct FIGAERO-I-CIMS varies by only ±50%, suggesting that EESI-TOF mass spectra indeed reflect the actual distribution of detectable compds. in the particle phase. Successful deployments of the EESI-TOF for lab. environmental chamber measurements, ground-based ambient sampling, and proof-of-concept measurements aboard a research aircraft highlight the versatility and potential of the EESI-TOF system.
  12. 12
    Lee, C. P.; Surdu, M.; Bell, D. M.; Lamkaddam, H.; Wang, M.; Ataei, F.; Hofbauer, V.; Lopez, B.; Donahue, N. M.; Dommen, J. Effects of Aerosol Size and Coating Thickness on the Molecular Detection using Extractive Electrospray Ionization. Atmos. Meas. Tech. 2021, 14, 5913– 5923,  DOI: 10.5194/amt-14-5913-2021
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    12
    Effects of aerosol size and coating thickness on the molecular detection using extractive electrospray ionization
    Lee, Chuan Ping; Surdu, Mihnea; Bell, David M.; Lamkaddam, Houssni; Wang, Mingyi; Ataei, Farnoush; Hofbauer, Victoria; Lopez, Brandon; Donahue, Neil M.; Dommen, Josef; Prevot, Andre S. H.; Slowik, Jay G.; Wang, Dongyu; Baltensperger, Urs; El Haddad, Imad
    Atmospheric Measurement Techniques (2021), 14 (9), 5913-5923CODEN: AMTTC2; ISSN:1867-8548. (Copernicus Publications)
    Extractive electrospray ionization (EESI) has been a well-known technique for high-throughput online mol. characterization of chem. reaction products and intermediates, detection of native biomols., in vivo metabolomics, and environmental monitoring with negligible thermal and ionization-induced fragmentation for over two decades. However, the EESI extn. mechanism remains uncertain. Here, we examd. the analyte extn. mechanism by assessing the influence of particle size and coating thickness on the detection of the mols. therein. We also found that the EESI sensitivity exhibited a strong size dependence, with an increase in sensitivity by 1-3 orders of magnitude as particle size decreased from 300 to 30 nm. This dependence varied with the electrospray (ES) droplet size, the particle size and the residence time for coagulation in the EESI inlet, suggesting that the EESI sensitivity was influenced by the coagulation coeff. between particles and ES droplets. Overall, our results indicate that, in the EESI, particles are fully extd. by the ES droplets regardless of the chem. compn., when they are collected by the ES droplets. However, their coalescence is not complete and depends strongly on their size. This size dependence is esp. relevant when EESI is used to probe size-varying particles as is the case in aerosol formation and growth studies with size ranges below 100 nm.
  13. 13
    Pospisilova, V.; Bell, D. M.; Lamkaddam, H.; Bertrand, A.; Wang, L.; Bhattu, D.; Zhou, X.; Dommen, J.; Prevot, A. S. H.; Baltensperger, U. Photodegradation of α-Pinene Secondary Organic Aerosol Dominated by Moderately Oxidized Molecules. Environ. Sci. Technol. 2021, 55, 6936– 6943,  DOI: 10.1021/acs.est.0c06752
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    13
    Photodegradation of α-pinene secondary organic aerosol dominated by moderately oxidized molecules
    Pospisilova, Veronika; Bell, David M.; Lamkaddam, Houssni; Bertrand, Amelie; Wang, Liwei; Bhattu, Deepika; Zhou, Xueqin; Dommen, Josef; Prevot, Andre S. H.; Baltensperger, Urs; El Haddad, Imad; Slowik, Jay G.
    Environmental Science & Technology (2021), 55 (10), 6936-6943CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    Atm. secondary org. aerosol (SOA) undergoes chem. and phys. changes when exposed to UV radiation, affecting the atm. lifetime of the involved mols. However, these photolytic processes remain poorly constrained. Here, we present a study aimed at characterizing, at a mol. level and in real time, the chem. compn. of α-pinene SOA exposed to UV-A light at 50% relative humidity in an atm. simulation chamber. Significant SOA mass loss is obsd. at high loadings (~ 100μg m-3), whereas the effect is less prevalent at lower loadings (~ 20μg m-3). For the vast majority of mols. measured by the extractive electrospray time-of-flight mass spectrometer, there is a fraction that is photoactive and decays when exposed to UV-A radiation and a fraction that appears photorecalcitrant. The mols. that are most photoactive contain between 4 and 6 oxygen atoms, while the more highly oxygenated compds. and dimers do not exhibit significant decay. Overall, photolysis results in a redn. of the volatility of SOA, which cannot be explained by simple evaporative losses but requires either a change in volatility related to changes in functional groups or a change in phys. parameters (i.e., viscosity).
  14. 14
    Surdu, M.; Pospisilova, V.; Xiao, M.; Wang, M.; Mentler, B.; Simon, M.; Stolzenburg, D.; Hoyle, C. R.; Bell, D. M.; Lee, C. P. Molecular characterization of ultrafine particles using extractive electrospray time-of-flight mass spectrometry. Environ. Sci.: Atmos. 2021, 1, 434– 448,  DOI: 10.1039/D1EA00050K
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    14
    Molecular characterization of ultrafine particles using extractive electrospray time-of-flight mass spectrometry
    Surdu, Mihnea; Pospisilova, Veronika; Xiao, Mao; Wang, Mingyi; Mentler, Bernhard; Simon, Mario; Stolzenburg, Dominik; Hoyle, Christopher R.; Bell, David M.; Lee, Chuan Ping; Lamkaddam, Houssni; Lopez-Hilfiker, Felipe; Ahonen, Lauri R.; Amorim, Antonio; Baccarini, Andrea; Chen, Dexian; Dada, Lubna; Duplissy, Jonathan; Finkenzeller, Henning; He, Xu-Cheng; Hofbauer, Victoria; Kim, Changhyuk; Kurten, Andreas; Kvashnin, Aleksandr; Lehtipalo, Katrianne; Makhmutov, Vladimir; Molteni, Ugo; Nie, Wei; Onnela, Antti; Petaja, Tuukka; Quelever, Lauriane L. J.; Tauber, Christian; Tome, Antonio; Wagner, Robert; Yan, Chao; Prevot, Andre S. H.; Dommen, Josef; Donahue, Neil M.; Hansel, Armin; Curtius, Joachim; Winkler, Paul M.; Kulmala, Markku; Volkamer, Rainer; Flagan, Richard C.; Kirkby, Jasper; Worsnop, Douglas R.; Slowik, Jay G.; Wang, Dongyu S.; Baltensperger, Urs; Haddad, Imad el
    Environmental Science: Atmospheres (2021), 1 (6), 434-448CODEN: ESANC9; ISSN:2634-3606. (Royal Society of Chemistry)
    Aerosol particles neg. affect human health while also having climatic relevance due to, for example, their ability to act as cloud condensation nuclei. Ultrafine particles (diam. Dp < 100 nm) typically comprise the largest fraction of the total no. concn., however, their chem. characterization is difficult because of their low mass. Using an extractive electrospray time-of-flight mass spectrometer (EESI-TOF), we characterize the mol. compn. of freshly nucleated particles from naphthalene and β-caryophyllene oxidn. products at the CLOUD chamber at CERN. We perform a detailed intercomparison of the org. aerosol chem. compn. measured by the EESI-TOF and an iodide adduct chem. ionization mass spectrometer equipped with a filter inlet for gases and aerosols (FIGAERO-I-CIMS). We also use an aerosol growth model based on the condensation of org. vapors to show that the chem. compn. measured by the EESI-TOF is consistent with the expected condensed oxidn. products. This agreement could be further improved by constraining the EESI-TOF compd.-specific sensitivity or considering condensed-phase processes. Our results show that the EESI-TOF can obtain the chem. compn. of particles as small as 20 nm in diam. with mass loadings as low as hundreds of ng m-3 in real time. This was until now difficult to achieve, as other online instruments are often limited by size cutoffs, ionization/thermal fragmentation and/or semi-continuous sampling. Using real-time simultaneous gas- and particle-phase data, we discuss the condensation of naphthalene oxidn. products on a mol. level.
  15. 15
    Patriarca, C.; Balderrama, A.; Može, M.; Sjöberg, P. J. R.; Bergquist, J.; Tranvik, L. J.; Hawkes, J. A. Investigating the Ionization of Dissolved Organic Matter by Electrospray. Anal. Chem. 2020, 92, 14210– 14218,  DOI: 10.1021/acs.analchem.0c03438
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    15
    Investigating the ionization of dissolved organic matter by electrospray
    Patriarca, Claudia; Balderrama, Andrea; Moze, Martina; Sjoeberg, Per J. R.; Bergquist, Jonas; Tranvik, Lars J.; Hawkes, Jeffrey A.
    Analytical Chemistry (Washington, DC, United States) (2020), 92 (20), 14210-14218CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)
    Electrospray ionization (ESI) operating in the neg. mode coupled to high-resoln. mass spectrometry is the most popular technique for the characterization of dissolved org. matter (DOM). The vast mol. heterogeneity and the functional group diversity of this complex mixt. prevents the efficient ionization of the org. material by a single ionization source, so the presence of uncharacterized material is unavoidable. The extent of this poorly ionizable pool of carbon is unknown, is presumably variable between samples, and can only be assessed by the combination of anal. with a uniform detection method. Charged aerosol detection (CAD), whose response is proportional to the amt. of nonvolatile material and is independent from the physicochem. properties of the analytes, is a suitable candidate. In this study, a fulvic acid mixt. was fractionated and analyzed by high-pressure liq. chromatog.-mass spectrometry in order to investigate the polarity and size distributions of highly and poorly ionizable material in the sample. Addnl., DOM samples of terrestrial and marine origins were analyzed to evaluate the variability of these pools across the land-sea aquatic continuum. The relative response factor values indicated that highly ionizable components of aquatic DOM mixts. are more hydrophilic and have lower mol. wt. than poorly ionizable components. Addnl., a discrepancy between the samples of terrestrial and marine origins was found, indicating that marine samples are better represented by ESI than terrestrial samples, which have an abundant portion of hydrophobic poorly ionizable material.
  16. 16
    The pre-publication history for this paper can be accessed here: http://www.biomedcentral.com/1471-2466/14/31/prepub.
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    There is no corresponding record for this reference.
    (a) Qi, L.; Chen, M.; Stefenelli, G.; Pospisilova, V.; Tong, Y.; Bertrand, A.; Hueglin, C.; Ge, X.; Baltensperger, U.; Prévôt, A. S. H. Organic aerosol source apportionment in Zurich using an extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF-MS) – Part 2: biomass burning influences in winter. Atmos. Chem. Phys. 2019, 19, 8037– 8062,  DOI: 10.5194/acp-19-8037-2019
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    16a
    Organic aerosol source apportionment in Zurich using an extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF-MS) - Part 2: biomass burning influences in winter
    Qi, Lu; Chen, Mindong; Stefenelli, Giulia; Pospisilova, Veronika; Tong, Yandong; Bertrand, Amelie; Hueglin, Christoph; Ge, Xinlei; Baltensperger, Urs; Prevot, Andre S. H.; Slowik, Jay G.
    Atmospheric Chemistry and Physics (2019), 19 (12), 8037-8062CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
    Real-time, in situ mol. compn. measurements of the org. fraction of fine particulate matter (PM2.5) remain challenging, hindering a full understanding of the climate impacts and health effects of PM2.5. In particular, the thermal decompn. and ionization-induced fragmentation affecting current techniques has limited a detailed investigation of secondary org. aerosol (SOA), which typically dominates OA. Here we deploy a novel extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF-MS) during winter 2017 in downtown Zurich, Switzerland, which overcomes these limitations, together with an Aerodyne high-resoln. time-of-flight aerosol mass spectrometer (HR-TOF-AMS) and supporting instrumentation. Pos. matrix factorization (PMF) implemented within the Multilinear Engine (ME-2) program was applied to the EESI-TOF-MS data to quantify the primary and secondary contributions to OA. An 11-factor soln. was selected as the best representation of the data, including five primary and six secondary factors. Primary factors showed influence from cooking, cigarette smoke, biomass burning (two factors) and a special local unknown event occurred only during two nights. Secondary factors were affected by biomass burning (three factors, distinguished by temp. and/or wind direction), organonitrates, monoterpene oxidn., and undetd. regional processing, in particular the contributions of wood combustion.
    (b) Stefenelli, G.; Pospisilova, V.; Lopez-Hilfiker, F. D.; Daellenbach, K. R.; Hüglin, C.; Tong, Y.; Baltensperger, U.; Prévôt, A. S. H.; Slowik, J. G. Organic aerosol source apportionment in Zurich using an extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF-MS) – Part 1: Biogenic influences and day–night chemistry in summer. Atmos. Chem. Phys. 2019, 19, 14825– 14848,  DOI: 10.5194/acp-19-14825-2019
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    16b
    Organic aerosol source apportionment in Zurich using an extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF-MS) - part 1: biogenic influences and day-night chemistry in summer
    Stefenelli, Giulia; Pospisilova, Veronika; Lopez-Hilfiker, Felipe D.; Daellenbach, Kaspar R.; Huglin, Christoph; Tong, Yandong; Baltensperger, Urs; Prevot, Andre S. H.; Slowik, Jay G.
    Atmospheric Chemistry and Physics (2019), 19 (23), 14825-14848CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
    Improving the understanding of the health and climate impacts of aerosols remains challenging and is restricted by the limitations of current measurement techniques. Detailed investigation of secondary org. aerosol (SOA), which is typically the dominating fraction of the org. aerosol (OA), requires instrumentation capable of real-time, in situ measurements of mol. compn. In this study, we present the first ambient measurements by a novel extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF-MS). The EESI-TOF-MS was deployed along with a high-resoln. time-of-flight aerosol mass spectrometer (HR-ToF-AMS) during summer 2016 at an urban location (Zurich, Switzerland). Pos. matrix factorization (PMF), implemented within the Multilinear Engine (ME-2), was applied to the data from both instruments to quantify the primary and secondary contributions to OA. From the EESI-TOF-MS anal., a six-factor soln. was selected as the most representative and interpretable soln. for the investigated dataset, including two primary and four secondary factors. The primary factors are dominated by cooking and cigarette smoke signatures while the secondary factors are discriminated according to their daytime (two factors) and night-time (two factors) chem. All four factors showed strong influence by biogenic emissions but exhibited significant day-night differences.
  17. 17
    Bell, D. M.; Wu, C.; Bertrand, A.; Graham, E.; Schoonbaert, J.; Giannoukos, S.; Baltensperger, U.; Prevot, A. S. H.; Riipinen, I.; El Haddad, I. Particle-phase processing of α-pinene NO3 secondary organic aerosol in the dark. Atmos. Chem. Phys. 2022, 22, 13167– 13182,  DOI: 10.5194/acp-22-13167-2022
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    17
    Particle-phase processing of α-pinene NO3 secondary organic aerosol in the dark
    Bell, David M.; Wu, Cheng; Bertrand, Amelie; Graham, Emelie; Schoonbaert, Janne; Giannoukos, Stamatios; Baltensperger, Urs; Prevot, Andre S. H.; Riipinen, Ilona; El Haddad, Imad; Mohr, Claudia
    Atmospheric Chemistry and Physics (2022), 22 (19), 13167-13182CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
    The NO3 radical represents a significant night time oxidant which is present downstream of polluted environments. Existing studies have investigated the formation of secondary org. aerosol (SOA) from NO3 radicals, focusing on the yields, general compn., and hydrolysis of organonitrates; however, there is limited knowledge about how the compn. of NO3-derived SOA evolves as a result of particle-phase reactions. Here, SOA was formed from the reaction of α-pinene with NO3 radicals generated from N2O5, and the resulting SOA was aged in the dark. The initial compn. of NO3-derived α-pinene SOA was slightly dependent upon the concn. of N2O5 injected (excess of NO3 or excess of α-pinene) but was largely dominated by dimer dinitrates (C20H32N2O8-13). Oxidn. reactions (e.g., C20H32N2O8 → C20H32N2O9 → C20H32N2O10) accounted for 60 %-70 % of the particle-phase reactions obsd. Fragmentation reactions and dimer degrdn. pathways made up the remainder of the particle-phase processes occurring. The exact oxidant is not known, although suggestions are offered (e.g., N2O5, org. peroxides, or peroxynitrates). Hydrolysis of -ONO2 functional groups was not an important loss term during dark aging under the relative humidity conditions of our expts. (58 %-62 %), and changes in the bulk organonitrate compn. were likely driven by evapn. of highly nitrogenated mols. Overall, 25 %-30 % of the particle-phase compn. changes as a function of particle-phase reactions during dark aging, representing an important atm. aging pathway.
  18. 18
    Liu, X.; Day, D. A.; Krechmer, J. E.; Brown, W.; Peng, Z.; Ziemann, P. J.; Jimenez, J. L. Direct measurements of semi-volatile organic compound dynamics show near-unity mass accommodation coefficients for diverse aerosols. Commun. Chem. 2019, 2, 98,  DOI: 10.1038/s42004-019-0200-x
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  19. 19
    Rovelli, G.; Jacobs, M. I.; Willis, M. D.; Rapf, R. J.; Prophet, A. M.; Wilson, K. R. A critical analysis of electrospray techniques for the determination of accelerated rates and mechanisms of chemical reactions in droplets. Chem. Sci. 2020, 11, 13026– 13043,  DOI: 10.1039/D0SC04611F
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    19
    A critical analysis of electrospray techniques for the determination of accelerated rates and mechanisms of chemical reactions in droplets
    Rovelli, Grazia; Jacobs, Michael I.; Willis, Megan D.; Rapf, Rebecca J.; Prophet, Alexander M.; Wilson, Kevin R.
    Chemical Science (2020), 11 (48), 13026-13043CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
    Electrospray and Electrosonic Spray Ionization Mass Spectrometry (ESI-MS and ESSI-MS) have been widely used to report evidence that many chem. reactions in micro- and nano-droplets are dramatically accelerated by factors of ~ 102 to 106 relative to macroscale bulk solns. Despite electrospray's relative simplicity to both generate and detect reaction products in charged droplets using mass spectrometry, substantial complexity exists in how the electrospray process itself impacts the interpretation of the mechanism of these obsd. accelerated rates. ESI and ESSI are both coupled multi-phase processes, in which analytes in small charged droplets are transferred and detected as gas-phase ions with a mass spectrometer. As such, quant. examn. is needed to evaluate the impact of multiple exptl. factors on the magnitude and mechanisms of reaction acceleration. These include: (1) evaporative concn. of reactants as a function of droplet size and initial concn., (2) competition from gas-phase chem. and reactions on exptl. surfaces, (3) differences in ionization efficiency and ion transmission and (4) droplet charge. We examine (1-4) using numerical models, new ESI/ESSI-MS exptl. data, and prior literature to assess the limitations of these approaches and the exptl. best practices required to robustly interpret acceleration factors in micro- and nano-droplets produced by ESI and ESSI.
  20. 20
    (a) Krieger, U. K.; Siegrist, F.; Marcolli, C.; Emanuelsson, E. U.; Gøbel, F. M.; Bilde, M.; Marsh, A.; Reid, J. P.; Huisman, A. J.; Riipinen, I. A reference data set for validating vapor pressure measurement techniques: homologous series of polyethylene glycols. Atmos. Meas. Tech. 2018, 11, 49– 63,  DOI: 10.5194/amt-11-49-2018
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    There is no corresponding record for this reference.
    (b) Ylisirniö, A.; Barreira, L. M. F.; Pullinen, I.; Buchholz, A.; Jayne, J.; Krechmer, J. E.; Worsnop, D. R.; Virtanen, A.; Schobesberger, S. On the calibration of FIGAERO-ToF-CIMS: importance and impact of calibrant delivery for the particle-phase calibration. Atmos. Meas. Tech. 2021, 14, 355– 367,  DOI: 10.5194/amt-14-355-2021
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    20b
    On the calibration of FIGAERO-ToF-CIMS: importance and impact of calibrant delivery for the particle-phase calibration
    Ylisirnio, Arttu; Barreira, Luis m. f.; Pullinen, Iida; Buchholz, Angela; Jayne, John; Krechmer, Jordan e.; Worsnop, Douglas r.; Virtanen, Annele; Schobesberger, Siegfried
    Atmospheric Measurement Techniques (2021), 14 (1), 355-367CODEN: AMTTC2; ISSN:1867-8548. (Copernicus Publications)
    The Filter Inlet for Gases and AEROsols (FIGAERO) coupled with a time-of-flight chem. ionization mass spectrometer (ToF-CIMS) enables online measurements of both gas-phase and particle-phase chem. constituents of ambient aerosols. When properly calibrated, the incorporated particle filter collection and subsequent thermal desorption enable the direct measurement of volatility of said constituents. Previously published volatility calibration results however differ from each other significantly. In this study we investigate the reason for this discrepancy. We found a major source of error in the widely used syringe deposition calibration method that can lead to an overestimation of satn. vapor pressures by several orders of magnitude. We propose a new method for volatility calibration by using atomized calibration compds. that more accurately captures the evapn. of chem. constituents from ambient aerosol particles. For example, we found a difference of ∼ 15°C in obsd. Tmax values between the atomizer method and syringe method using the lowest soln. concn. (0.003 g L-1). This difference translates into a difference of up to 3 orders of magnitude in satn. concn. C* space. We justify our claim with evapn. modeling and direct SEM imaging, while also presenting possible error sources of the atomizer method. We finally present how typical calibration parameters derived with both methods impact the volatility basis set (VBS) derived from measurements of secondary org. aerosols (SOAs).
  21. 21
    (a) Bell, D. M.; Imre, D.; T Martin, S.; Zelenyuk, A. The properties and behavior of α-pinene secondary organic aerosol particles exposed to ammonia under dry conditions. Phys. Chem. Chem. Phys. 2017, 19, 6497– 6507,  DOI: 10.1039/C6CP08839B
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    21a
    The properties and behavior of α-pinene secondary organic aerosol particles exposed to ammonia under dry conditions
    Bell, David M.; Imre, Dan; T. Martin, Scot; Zelenyuk, Alla
    Physical Chemistry Chemical Physics (2017), 19 (9), 6497-6507CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
    Chem. transformations and aging of secondary org. aerosol (SOA) particles can alter their phys. and chem. properties, including particle morphol. Ammonia, one of the common atm. reactive constituents, can react with SOA particles, changing their properties and behavior. At low relative humidity, NH3 uptake by α-pinene SOA particles appears to be limited to the particle surface, which suggests that the reacted particles might not be homogeneous and have complex morphol. Here, we present a study aimed at detailed characterization of the effect of ammonia on the compn., d., morphol., shape, and evapn. kinetics of α-pinene SOA particles. We find that a small amt. of NH3 diffuses and reacts throughout the particle bulk, while most of the ammoniated products result from the reaction of NH3 with carboxylic acids on the particle surface, leading to a slight increase in particle size. We show that the reaction products form a solid semi-volatile coating that is a few nanometers thick. This solid coating prevents coagulating particles from coalescing for over two days. However, when the gas phase is dild. this semi-volatile coating evaps. in minutes, which is ensued by rapid coalescence. The ammoniated products in the particle bulk affect particles' evapn. kinetics, more so for the smaller particles that contain a higher fraction of ammoniated products.
    (b) Wilson, J.; Imre, D.; Beránek, J.; Shrivastava, M.; Zelenyuk, A. Evaporation Kinetics of Laboratory-Generated Secondary Organic Aerosols at Elevated Relative Humidity. Environ. Sci. Technol. 2015, 49, 243– 249,  DOI: 10.1021/es505331d
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    21b
    Evaporation Kinetics of Laboratory-Generated Secondary Organic Aerosols at Elevated Relative Humidity
    Wilson, Jacqueline; Imre, Dan; Beranek, Josef; Shrivastava, Manish; Zelenyuk, Alla
    Environmental Science & Technology (2015), 49 (1), 243-249CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    Secondary org. aerosols (SOA) dominate atm. org. aerosols which affect climate, air quality, and health. Recent studies indicated that contrary to previously held assumptions, at low relative humidity (RH) these particles are semi-solid and evap. orders of magnitude slower than expected. Elevated relative humidity has the potential to significantly affect formation, properties, and atm. evolution of SOA particles. This work assessed the effect of RH on room temp. evapn. kinetics of SOA particles formed by ozonolysis of α-pinene and limonene. Expts. were conducted on α-pinene SOA particles generated, evapd., and aged at <5, 50, and 90% RH, and on limonene SOA particles at <5 and 90% RH. In all cases, evapn. began with a relatively fast phase, during which 30-70% of the particle mass evapd. in 2 h, followed by a much slower evapn. rate. Evapn. kinetics at <5 and 50% RH were nearly the same; at 90% RH, a slightly larger fraction evapd. In all cases, particle aging prior to induced evapn. reduced evaporative losses; aging at elevated RH led to a more significant effect. In all cases, obsd. SOA evapn. was nearly size-independent.
  22. 22
    Vaden, T. D.; Imre, D.; Beranek, J.; Shrivastava, M.; Zelenyuk, A. Evaporation kinetics and phase of laboratory and ambient secondary organic aerosol. Proc. Natl. Acad. Sci. U.S.A. 2011, 108, 2190– 2195,  DOI: 10.1073/pnas.1013391108
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    22
    Evaporation kinetics and phase of laboratory and ambient secondary organic aerosol
    Vaden, Timothy D.; Imre, Dan; Beranek, Josef; Shrivastava, Manish; Zelenyuk, Alla
    Proceedings of the National Academy of Sciences of the United States of America (2011), 108 (6), 2190-2195, S2190/1-S2190/5CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)
    Field measurements of secondary org. aerosols (SOA) demonstrate significantly higher mass loads than those predicted by models, creating an intense effort focused on detg. addnl. SOA sources but leaving fundamental model assumptions unchallenged. Existing air quality models use absorptive partitioning theory and assume SOA particles are liq. droplets, forming an instantaneous reversible equil. with the gas phase. They ignore the effect of spectator org. species adsorption during SOA formation on SOA properties and fate. Using an accurate, highly sensitive exptl. approach to examine evapn. kinetics of size-selected, single SOA particles, the authors characterized room temp. evapn. kinetics of lab.-generated α-pinene and ambient atm. SOA. Even when gas phase orgs. were removed, it takes ∼24 h for pure α-pinene SOA particles to evap. 75% of their mass; this is in sharp contrast to the ∼10 min time scale predicted by existing kinetic models. Spectator org. vapor adsorption during SOA formation and the aging of these coated SOA particles dramatically reduced the evapn. rate; in some cases it nearly stopped it. Ambient SOA exhibited evapn. behavior very similar to that of lab.-generated, coated and aged SOA. For all cases assessed in this work, SOA evapn. behavior was nearly size-independent and did not follow evapn. kinetics of liq. droplets, in sharp contrast with model assumptions. Results concerning SOA phase, evapn. rate, and the importance of spectator gases and aging all indicated there is a need to reformulate the way SOA formation and evapn. are treated in models.
  23. 23
    Platt, S. M.; El Haddad, I.; Zardini, A. A.; Clairotte, M.; Astorga, C.; Wolf, R.; Slowik, J. G.; Temime-Roussel, B.; Marchand, N.; Ježek, I. Secondary organic aerosol formation from gasoline vehicle emissions in a new mobile environmental reaction chamber. Atmos. Chem. Phys. 2013, 13, 9141– 9158,  DOI: 10.5194/acp-13-9141-2013
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    23
    Secondary organic aerosol formation from gasoline vehicle emissions in a new mobile environmental reaction chamber
    Platt, S. M.; El Haddad, I.; Zardini, A. A.; Clairotte, M.; Astorga, C.; Wolf, R.; Slowik, J. G.; Temime-Roussel, B.; Marchand, N.; Jezek, I.; Drinovec, L.; Mocnik, G.; Moehler, O.; Richter, R.; Barmet, P.; Bianchi, F.; Baltensperger, U.; Prevot, A. S. H.
    Atmospheric Chemistry and Physics (2013), 13 (18), 9141-9158, 18 pp.CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
    We present a new mobile environmental reaction chamber for the simulation of the atm. aging of different emission sources without limitation from the instruments or facilities available at any single site. Photochem. is simulated using a set of 40 UV lights (total power 4 KW). Characterization of the emission spectrum of these lights shows that atm. aging of emissions may be simulated over a range of temps. (-7 to 25 °C). A photolysis rate of NO2, JNO2, of (8.0 ± 0.7) × 10-3 s-1 was detd. at 25°C. We demonstrate the utility of this new system by presenting results on the aging (OH = 12 × 106 cm-3 h) of emissions from a modern (Euro 5) gasoline car operated during a driving cycle (New European Driving Cycle, NEDC) on a chassis dynamometer in a vehicle test cell. Emissions from the entire NEDC were sampled and aged in the chamber. Total org. aerosol (OA; primary org. aerosol (POA) emission + secondary org. aerosol (SOA) formation) was (369.8-397.5) 10-3 g kg-1 fuel, or (13.2-15.4) × 10-3 g km-1, after aging, with aged OA/POA in the range 9-15. A thorough investigation of the compn. of the gas phase emissions suggests that the obsd. SOA is from previously unconsidered precursors and processes. This large enhancement in particulate matter mass from gasoline vehicle aerosol emissions due to SOA formation, if it occurs across a wider range of gasoline vehicles, would have significant implications for our understanding of the contribution of on-road gasoline vehicles to ambient aerosols.
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    Cation-ether complexes in the gas phase: thermodynamic insight into molecular recognition
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    Trends in the bond dissocn. energies for the binding of the alkali metal cations, Li+, Na+, K+, Rb+, and Cs+, to a series of ethers, 1-4 di-Me ethers, 1 and 2 dimethoxy ethanes, and the crown ethers, 12c4, 15c5, and 18c6, are discussed. The bond energies have been detd. in previous studies by anal. of the thresholds for collision-induced dissocn. of the cation-ether complexes by xenon as measured in a guided ion beam tandem mass spectrometer. Details of the anal. of the data are reviewed and the accuracy of the results ascertained by comparison with theor. results taken from the literature. Combined, the exptl. and theor. results provide an extensive thermochem. database for evaluation of the metal-crown complexes, a simple example of mol. recognition. These results indicate the importance of optimizing the metal-oxygen bond distances and the orientation of the local dipole on the oxygen towards the metal. Further, it is shown that excited state conformers of these complexes are probably obsd. in several systems as a result of interesting metal-dependent dynamics in the formation of the complexes.
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    Bond dissocn. energies of Na+[O(CH3)2]x, x = 1-4; Na+[(CH2OCH3)2]x, x = 1 and 2; and Na+[c-(C2H4O)4] are reported. The bond dissocn. energies are detd. exptl. by anal. of the thresholds for collision-induced dissocn. of the cation-ether complexes by xenon measured using guided ion beam mass spectrometry. In all cases, the primary and lowest energy dissocn. channel obsd. exptl. is endothermic loss of one ligand mol. The cross section thresholds are interpreted to yield 0 and 298 K bond dissocn. energies after accounting for the effects of multiple ion-mol. collisions, internal energy of the complexes, and unimol. decay rates. Trends in the bond dissocn. energies detd. by expt. and recent theor. ab initio calcns. are in good agreement. Our best exptl. values, which have an av. uncertainty of ±7 kJ/mol, are lower than the theor. values by 7 ± 5 kJ/mol per metal-oxygen interaction. These values are compared with bond dissocn. energies for the comparable lithium cation-ether complexes. This comparison reveals the thermodn. consequences of ligand-ligand repulsion.
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    Lee, C. P.; Surdu, M.; Bell, D. M.; Dommen, J.; Xiao, M.; Zhou, X.; Baccarini, A.; Giannoukos, S.; Wehrle, G.; Schneider, P. A. High-frequency gaseous and particulate chemical characterization using extractive electrospray ionization mass spectrometry (Dual-Phase-EESI-TOF). Atmos. Meas. Tech. 2022, 15, 3747– 3760,  DOI: 10.5194/amt-15-3747-2022
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    High-frequency gaseous and particulate chemical characterization using extractive electrospray ionization mass spectrometry (Dual-Phase-EESI-TOF)
    Lee, Chuan Ping; Surdu, Mihnea; Bell, David M.; Dommen, Josef; Xiao, Mao; Zhou, Xueqin; Baccarini, Andrea; Giannoukos, Stamatios; Wehrle, Gunther; Schneider, Pascal Andre; Prevot, Andre S. H.; Slowik, Jay G.; Lamkaddam, Houssni; Wang, Dongyu; Baltensperger, Urs; El Haddad, Imad
    Atmospheric Measurement Techniques (2022), 15 (12), 3747-3760CODEN: AMTTC2; ISSN:1867-8548. (Copernicus Publications)
    To elucidate the sources and chem. reaction pathways of org. vapors and particulate matter in the ambient atm., real-time detection of both the gas and particle phase is needed. State-of-the-art techniques often suffer from thermal decompn., ionization-induced fragmentation, high cut-off size of aerosols or low time resoln. In response to all these limitations, we developed a new technique that uses extractive electrospray ionization (EESI) for online gas and particle chem. speciation, namely the dual-phase extractive electrospray ionization time-of-flight mass spectrometer (Dual-Phase-EESI-TOF or Dual-EESI for short). The Dual-EESI was designed and optimized to measure gas- and particle-phase species with satn. vapor concns. spanning more than 10 orders of magnitude with good linearity and a measurement cycle as fast as 3 min. The gas-phase selectivity of the Dual-EESI was compared with that of nitrate chem. ionization mass spectrometry. In addn., we performed org. aerosol uptake expts. to characterize the relative gas and particle response factors. In general, the Dual-EESI is more sensitive toward gas-phase analytes as compared to their particle-phase counterparts. The real-time measurement capability of the Dual-EESI for chem. speciated gas- and particle-phase measurements can provide new insights into aerosol sources or formation mechanisms, where gas-particle partitioning behavior can be detd. after abs. parameterization of the gas / particle sensitivity.
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    Clark, C. H.; Nakao, S.; Asa-Awuku, A.; Sato, K.; Cocker, D. R. Real-Time Study of Particle-Phase Products from α-Pinene Ozonolysis and Isoprene Photooxidation Using Particle into Liquid Sampling Directly Coupled to a Time-of-Flight Mass Spectrometer (PILS-ToF). Aerosol Sci. Technol. 2013, 47, 1374– 1382,  DOI: 10.1080/02786826.2013.844333
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    A particle into liq. sampler (PILS) has been directly coupled to an accurate mass atm. ionization time-of-flight mass spectrometer (TOF) for use in the speciation of secondary org. aerosol (SOA) formed in the University of California-Riverside, College of Engineering-Center for Environmental Research and Technol. (CE-CERT) atm. chambers. To this end, the PILS has been optimized for direct continuous injection into the ToF and the PILS-ToF system has been used to obtain real-time mass spectral traces of the particle phase products of atm. chamber reactions. The PILS-ToF system has been initially applied to SOA formed from α-pinene dark ozonolysis and isoprene photooxidn. The characterization of the PILS-TOF system includes expts. on the well understood α-pinene/O3 system, which verifies the performance of the tool. The PILS-TOF tool is then used to provide new insight into the chem. compn. of the SOA formed from isoprene photooxidn. For the first time, time resolved traces of oligomer formation during isoprene photooxidn. are obsd. using the PILS-TOF. The unique subunits of oligomer series are reported. The PILS-TOF system is demonstrated to be a powerful tool for obtaining real-time electro spray ionization and chem. ionization mass spectral speciation of aerosols.Copyright 2013 American Assocn. for Aerosol Research.
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    Formation of secondary org. aerosols (SOA) from biogenic volatile org. compds. (BVOC) occurs via O3- and OH-initiated reactions during the day and reactions with NO3 during the night. We explored the effect of these three oxidn. conditions on the mol. compn. and aq. photochem. of model SOA prepd. from two common BVOC. A common monoterpene, α-pinene, and sesquiterpene, α-humulene, were used to form SOA in a smog chamber via BVOC + O3, BVOC + NO3, and BVOC + OH + NOx oxidn. Samples of SOA were collected on filters, water-sol. compds. from SOA were extd. in water, and the resulting aq. solns. were photolyzed to simulate the photochem. aq. processing of SOA. The extent of change in the mol. level compn. of SOA over 4 h of photolysis (approx. equiv. to 64 h of photolysis under ambient conditions) was assessed with high-resoln. electrospray ionization mass spectrometry. The anal. revealed significant differences in the mol. compn. between SOA formed by the different oxidn. pathways. The compn. further evolved during photolysis with the most notable change corresponding to the nearly complete removal of nitrogen-contg. org. compds. Hydrolysis of SOA compds. also occurred in parallel with photolysis. The preferential loss of larger SOA compds. during photolysis and hydrolysis made the SOA compds. more volatile on av. This study suggests that aq. processes may under certain conditions lead to a redn. in the SOA loading as opposed to an increase in SOA loading commonly assumed in the literature.
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  • Abstract

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    Figure 1

    Figure 1. (A) Mass spectrum of PEG-300 as measured by the EESI. (B) Fraction remaining of each PEG measured by the EESI as a function of TD temperature, from triplicates. (C) A single measurement showing absolute mass concentration (left-axis) measured by the SMPS, EESI mass flux (red axis, right side), and for the EESI sensitivity using the mid-point temperatures (blue axis, right side), and the error bars correspond to the error propagated using the measured standard error.

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    Figure 2

    Figure 2. (A) EESI sensitivity determined from bulk standards compared to the bulk TD method and iterative-TD sensitivities (left-axis). Binding energies are shown for each PEG (right-axis). (B) Composition of PEG-300 without correction (blue) compared to the composition after correction based on EESI sensitivity (orange).

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    Figure 3

    Figure 3. (A) Mass spectrum from α-pinene SOA measured by the EESI. (B) Mass defect plot of the same mass spectrum. Trimers highlighted in orange, tetramers highlighted in green.

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    Figure 4

    Figure 4. (A) Fraction remaining of the SMPS mass concentration (size distributions are found in Figure S7), EESI measured composition, and aggregated classes of α-pinene SOA (from triplicate measurements). (B) Relative fraction of species evaporating between TD steps for a single measurement.

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    Figure 5

    Figure 5. (A) Sensitivity for the different molecular classes of α-pinene SOA based on bulk sensitivities (initial guess) and after the iterative solution. (B) Relative contribution of each molecular class before and after the sensitivity correction using the iterative solution.

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  • References

    This article references 27 other publications.

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      A review. Summary: Aerosolised drugs are prescribed for use in a range of inhaler devices and systems. Delivering drugs by inhalation requires a formulation that can be successfully aerosolised and a delivery system that produces a useful aerosol of the drug; the particles or droplets need to be of sufficient size and mass to be carried to the distal lung or deposited on proximal airways to give rise to a therapeutic effect. Patients and caregivers must use and maintain these aerosol drug delivery devices correctly. In recent years, several tech. innovations have led to aerosol drug delivery devices with efficient drug delivery and with novel features that take into account factors such as dose tracking, portability, materials of manuf., breath actuation, the interface with the patient, combination therapies, and systemic delivery. These changes have improved performance in all four categories of devices: metered dose inhalers, spacers and holding chambers, dry powder inhalers, and nebulisers. Addnl., several therapies usually given by injection are now prescribed as aerosols for use in a range of drug delivery devices. In this Review, we discuss recent developments in the design and clin. use of aerosol devices over the past 10-15 years with an emphasis on the treatment of respiratory disorders.
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      Journal of Controlled Release (2020), 325 (), 276-292CODEN: JCREEC; ISSN:0168-3659. (Elsevier B.V.)
      A review. The rise of antimicrobial resistance has created an urgent need for the development of new methods for antibiotics delivery to patients with pulmonary infections in order to mainly increase the effectiveness of the drugs administration, to minimize the risk of emergence of resistant strains, and to prevent patients reinfection. Since bacterial resistance is often related to antibiotic concn., their pulmonary administration could eradicate strains resistant to the same drug at the concn. achieved through the systemic circulation. Pulmonary administration offers several advantages; it directly targets the site of the infection which allows the inhaled dose of the drug to be reduced compared to that administered orally or parenterally while keeping the same local effect. The review article is made with an objective to compile information about various existing modern technologies developed to provide greater patient compliance and reduce the undesirable side effect of the drugs. In conclusion, aerosol antibiotic delivery appears as one of the best technologies for the treatment of pulmonary infectious diseases and able to limit the systemic adverse effects related to the high drug dose and to make life easier for the patients.
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      Daellenbach, K. R.; Uzu, G.; Jiang, J.; Cassagnes, L.-E.; Leni, Z.; Vlachou, A.; Stefenelli, G.; Canonaco, F.; Weber, S.; Segers, A. Sources of particulate-matter air pollution and its oxidative potential in Europe. Nature 2020, 587, 414– 419,  DOI: 10.1038/s41586-020-2902-8
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      Sources of particulate-matter air pollution and its oxidative potential in Europe
      Daellenbach, Kaspar R.; Uzu, Gaelle; Jiang, Jianhui; Cassagnes, Laure-Estelle; Leni, Zaira; Vlachou, Athanasia; Stefenelli, Giulia; Canonaco, Francesco; Weber, Samuel; Segers, Arjo; Kuenen, Jeroen J. P.; Schaap, Martijn; Favez, Olivier; Albinet, Alexandre; Aksoyoglu, Sebnem; Dommen, Josef; Baltensperger, Urs; Geiser, Marianne; El Haddad, Imad; Jaffrezo, Jean-Luc; Prevot, Andre S. H.
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      Abstr.: Particulate matter is a component of ambient air pollution that has been linked to millions of annual premature deaths globally1-3. Assessments of the chronic and acute effects of particulate matter on human health tend to be based on mass concn., with particle size and compn. also thought to play a part4. Oxidative potential has been suggested to be one of the many possible drivers of the acute health effects of particulate matter, but the link remains uncertain5-8. Studies investigating the particulate-matter components that manifest an oxidative activity have yielded conflicting results7. In consequence, there is still much to be learned about the sources of particulate matter that may control the oxidative potential concn.7. Here we use field observations and air-quality modeling to quantify the major primary and secondary sources of particulate matter and of oxidative potential in Europe. We find that secondary inorg. components, crustal material and secondary biogenic org. aerosols control the mass concn. of particulate matter. By contrast, oxidative potential concn. is assocd. mostly with anthropogenic sources, in particular with fine-mode secondary org. aerosols largely from residential biomass burning and coarse-mode metals from vehicular non-exhaust emissions. Our results suggest that mitigation strategies aimed at reducing the mass concns. of particulate matter alone may not reduce the oxidative potential concn. If the oxidative potential can be linked to major health impacts, it may be more effective to control specific sources of particulate matter rather than overall particulate mass.
    4. 4
      Wang, D. S.; Lee, C. P.; Krechmer, J. E.; Majluf, F.; Tong, Y.; Canagaratna, M. R.; Schmale, J.; Prévôt, A. S. H.; Baltensperger, U.; Dommen, J. Constraining the response factors of an extractive electrospray ionization mass spectrometer for near-molecular aerosol speciation. Atmos. Meas. Tech. 2021, 14, 6955– 6972,  DOI: 10.5194/amt-14-6955-2021
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      Constraining the response factors of an extractive electrospray ionization mass spectrometer for near-molecular aerosol speciation
      Wang, Dongyu S.; Lee, Chuan Ping; Krechmer, Jordan E.; Majluf, Francesca; Tong, Yandong; Canagaratna, Manjula R.; Schmale, Julia; Prevot, Andre S. H.; Baltensperger, Urs; Dommen, Josef; El Haddad, Imad; Slowik, Jay G.; Bell, David M.
      Atmospheric Measurement Techniques (2021), 14 (11), 6955-6972CODEN: AMTTC2; ISSN:1867-8548. (Copernicus Publications)
      Online characterization of aerosol compn. at the near-mol. level is key to understanding chem. reaction mechanisms, kinetics, and sources under various atm. conditions. The recently developed extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF) is capable of detecting a wide range of org. oxidn. products in the particle phase in real time with minimal fragmentation. Quantification can sometimes be hindered by a lack of available com. stds. for aerosol constituents, however. Good correlations between the EESI-TOF and other aerosol speciation techniques have been reported, though no attempts have yet been made to parameterize the EESI-TOF response factor for different chem. species. Here, we report the first parameterization of the EESI-TOF response factor for secondary org. aerosol (SOA) at the near-mol. level based on its elemental compn. SOA was formed by ozonolysis of monoterpene or OH oxidn. of aroms. inside an oxidn. flow reactor (OFR) using ammonium nitrate as seed particles. A Vocus proton-transfer reaction mass spectrometer (Vocus-PTR) and a high-resoln. aerosol mass spectrometer (AMS) were used to det. the gas-phase mol. compn. and the particle-phase bulk chem. compn., resp. The EESI response factors towards bulk SOA coating and the inorg. seed particle core were constrained by intercomparison with the AMS. The highest bulk EESI response factor was obsd. for SOA produced from 1,3,5-trimethylbenzene, followed by those produced from d-limonene and o-cresol, consistent with previous findings. The near-mol. EESI response factors were derived from intercomparisons with VocusPTR measurements and were found to vary from 103 to 106 ion counts s-1 ppb-1, mostly within ±1 order of magnitude of their geometric mean of 104.6 ion counts s-1 ppb-1. For arom. SOA components, the EESI response factors correlated with mol. wt. and oxygen content and inversely correlated with volatility. The near-mol. response factors mostly agreed within a factor of 20 for isomers obsd. across the aroms. and biogenic systems. Parameterization of the near-mol. response factors based on the measured elemental formulas could reproduce the empirically detd. response factor for a single volatile org. compd. (VOC) system to within a factor of 5 for the configuration of our mass spectrometers. The results demonstrate that std.-free quantification using the EESI-TOF is possible.
    5. 5
      Jimenez, J. L.; Canagaratna, M. R.; Donahue, N. M.; Prevot, A. S. H.; Zhang, Q.; Kroll, J. H.; DeCarlo, P. F.; Allan, J. D.; Coe, H.; Ng, N. L. Evolution of Organic Aerosols in the Atmosphere. Science 2009, 326, 1525– 1529,  DOI: 10.1126/science.1180353
      5
      Evolution of Organic Aerosols in the Atmosphere
      Jimenez, J. L.; Canagaratna, M. R.; Donahue, N. M.; Prevot, A. S. H.; Zhang, Q.; Kroll, J. H.; DeCarlo, P. F.; Allan, J. D.; Coe, H.; Ng, N. L.; Aiken, A. C.; Docherty, K. S.; Ulbrich, I. M.; Grieshop, A. P.; Robinson, A. L.; Duplissy, J.; Smith, J. D.; Wilson, K. R.; Lanz, V. A.; Hueglin, C.; Sun, Y. L.; Tian, J.; Laaksonen, A.; Raatikainen, T.; Rautiainen, J.; Vaattovaara, P.; Ehn, M.; Kulmala, M.; Tomlinson, J. M.; Collins, D. R.; Cubison, M. J.; Dunlea, J.; Huffman, J. A.; Onasch, T. B.; Alfarra, M. R.; Williams, P. I.; Bower, K.; Kondo, Y.; Schneider, J.; Drewnick, F.; Borrmann, S.; Weimer, S.; Demerjian, K.; Salcedo, D.; Cottrell, L.; Griffin, R.; Takami, A.; Miyoshi, T.; Hatakeyama, S.; Shimono, A.; Sun, J. Y.; Zhang, Y. M.; Dzepina, K.; Kimmel, J. R.; Sueper, D.; Jayne, J. T.; Herndon, S. C.; Trimborn, A. M.; Williams, L. R.; Wood, E. C.; Middlebrook, A. M.; Kolb, C. E.; Baltensperger, U.; Worsnop, D. R.
      Science (Washington, DC, United States) (2009), 326 (5959), 1525-1529CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
      Org. aerosol (OA) particles affect climate forcing and human health, but their sources and evolution are poorly characterized. A unifying model framework describing the atm. evolution of OA which is constrained by high time resolved measurements of its compn., volatility, and oxidn. state is presented. OA and OA precursor gases evolve by becoming increasingly oxidized, less volatile, and more hygroscopic, leading to the formation of oxygenated org. aerosols (OOA), with concns. comparable to those of SO42- aerosols throughout the Northern Hemisphere. This model framework captures the dynamic aging behavior obsd. in the atm. and lab.; it serves as a basis to improve regional and global model parameterizations.
    6. 6
      (a) Mohr, C.; Thornton, J. A.; Heitto, A.; Lopez-Hilfiker, F. D.; Lutz, A.; Riipinen, I.; Hong, J.; Donahue, N. M.; Hallquist, M.; Petäjä, T. Molecular identification of organic vapors driving atmospheric nanoparticle growth. Nat. Commun. 2019, 10, 4442,  DOI: 10.1038/s41467-019-12473-2
      6a
      Molecular identification of organic vapors driving atmospheric nanoparticle growth
      Mohr, Claudia; Thornton, Joel A.; Heitto, Arto; Lopez-Hilfiker, Felipe D.; Lutz, Anna; Riipinen, Ilona; Hong, Juan; Donahue, Neil M.; Hallquist, Mattias; Petaejae, Tuukka; Kulmala, Markku; Yli-Juuti, Taina
      Nature Communications (2019), 10 (1), 4442CODEN: NCAOBW; ISSN:2041-1723. (Nature Research)
      Particles formed in the atm. via nucleation provide about half the no. of atm. cloud condensation nuclei, but in many locations, this process is limited by the growth of the newly formed particles. That growth is often via condensation of org. vapors. Identification of these vapors and their sources is thus fundamental for simulating changes to aerosol-cloud interactions, which are one of the most uncertain aspects of anthropogenic climate forcing. Here we present direct mol.-level observations of a distribution of org. vapors in a forested environment that can explain simultaneously obsd. atm. nanoparticle growth from 3 to 50 nm. Furthermore, the volatility distribution of these vapors is sufficient to explain nanoparticle growth without invoking particle-phase processes. The agreement between obsd. mass growth, and the growth predicted from the obsd. mass of condensing vapors in a forested environment thus represents an important step forward in the characterization of atm. particle growth.
      (b) Stolzenburg, D.; Fischer, L.; Vogel, A. L.; Heinritzi, M.; Schervish, M.; Simon, M.; Wagner, A. C.; Dada, L.; Ahonen, L. R.; Amorim, A. Rapid growth of organic aerosol nanoparticles over a wide tropospheric temperature range. Proc. Natl. Acad. Sci. U.S.A. 2018, 115, 9122– 9127,  DOI: 10.1073/pnas.1807604115
      6b
      Rapid growth of organic aerosol nanoparticles over a wide tropospheric temperature range
      Stolzenburg, Dominik; Fischer, Lukas; Vogel, Alexander L.; Heinritzi, Martin; Schervish, Meredith; Simon, Mario; Wagner, Andrea C.; Dada, Lubna; Ahonen, Lauri R.; Amorim, Antonio; Baccarini, Andrea; Bauer, Paulus S.; Baumgartner, Bernhard; Bergen, Anton; Bianchi, Federico; Breitenlechner, Martin; Brilke, Sophia; Mazon, Stephany Buenrostro; Chen, Dexian; Dias, AntA3nio; Draper, Danielle C.; Duplissy, Jonathan; El Haddad, Imad; Finkenzeller, Henning; Frege, Carla; Fuchs, Claudia; Garmash, Olga; Gordon, Hamish; He, Xucheng; Helm, Johanna; Hofbauer, Victoria; Hoyle, Christopher R.; Kim, Changhyuk; Kirkby, Jasper; Kontkanen, Jenni; KA1/4rten, Andreas; Lampilahti, Janne; Lawler, Michael; Lehtipalo, Katrianne; Leiminger, Markus; Mai, Huajun; Mathot, Serge; Mentler, Bernhard; Molteni, Ugo; Nie, Wei; Nieminen, Tuomo; Nowak, John B.; Ojdanic, Andrea; Onnela, Antti; Passananti, Monica; PetAjA, Tuukka; J. QuAlAver, Lauriane L.; Rissanen, Matti P.; Sarnela, Nina; Schallhart, Simon; Tauber, Christian; TomA, AntA3nio; Wagner, Robert; Wang, Mingyi; Weitz, Lena; Wimmer, Daniela; Xiao, Mao; Yan, Chao; Ye, Penglin; Zha, Qiaozhi; Baltensperger, Urs; Curtius, Joachim; Dommen, Josef; Flagan, Richard C.; Kulmala, Markku; Smith, James N.; Worsnop, Douglas R.; Hansel, Armin; Donahue, Neil M.; Winkler, Paul M.
      Proceedings of the National Academy of Sciences of the United States of America (2018), 115 (37), 9122-9127CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)
      Nucleation and growth of aerosol particles from atm. vapors constitutes a major source of global cloud condensation nuclei (CCN). The fraction of newly formed particles that reaches CCN sizes is highly sensitive to particle growth rates, esp. for particle sizes <10 nm, where coagulation losses to larger aerosol particles are greatest. Recent results show that some oxidn. products from biogenic volatile org. compds. are major contributors to particle formation and initial growth. However, whether oxidized orgs. contribute to particle growth over the broad span of tropospheric temps. remains an open question, and quant. mass balance for org. growth has yet to be demonstrated at any temp. Here, in expts. performed under atm. conditions in the Cosmics Leaving Outdoor Droplets (CLOUD) chamber at the European Organization for Nuclear Research (CERN), we show that rapid growth of org. particles occurs over the range from -25°C to 25°C. The lower extent of autoxidn. at reduced temps. is compensated by the decreased volatility of all oxidized mols. This is confirmed by particle-phase compn. measurements, showing enhanced uptake of relatively less oxygenated products at cold temps. We can reproduce the measured growth rates using an aerosol growth model based entirely on the exptl. measured gas-phase spectra of oxidized org. mols. obtained from two complementary mass spectrometers. We show that the growth rates are sensitive to particle curvature, explaining widespread atm. observations that particle growth rates increase in the single-digit-nanometer size range. Our results demonstrate that org. vapors can contribute to particle growth over a wide range of tropospheric temps. from mol. cluster sizes onward.
    7. 7
      (a) Simon, M.; Dada, L.; Heinritzi, M.; Scholz, W.; Stolzenburg, D.; Fischer, L.; Wagner, A. C.; Kürten, A.; Rörup, B.; He, X. C. Molecular understanding of new-particle formation from &lt;i&amp;gt;α&lt;/i&amp;gt;-pinene between −50 and +25 °C. Atmos. Chem. Phys. 2020, 20, 9183– 9207,  DOI: 10.5194/acp-20-9183-2020
      7a
      Molecular understanding of new-particle formation from α-pinene between -50 and +25 °C
      Simon, Mario; Dada, Lubna; Heinritzi, Martin; Scholz, Wiebke; Stolzenburg, Dominik; Fischer, Lukas; Wagner, Andrea C.; Kuerten, Andreas; Roerup, Birte; He, Xu-Cheng; Almeida, Joao; Baalbaki, Rima; Baccarini, Andrea; Bauer, Paulus S.; Beck, Lisa; Bergen, Anton; Bianchi, Federico; Braekling, Steffen; Brilke, Sophia; Caudillo, Lucia; Chen, Dexian; Chu, Biwu; Dias, Antonio; Draper, Danielle C.; Duplissy, Jonathan; El-Haddad, Imad; Finkenzeller, Henning; Frege, Carla; Gonzalez-Carracedo, Loic; Gordon, Hamish; Granzin, Manuel; Hakala, Jani; Hofbauer, Victoria; Hoyle, Christopher R.; Kim, Changhyuk; Kong, Weimeng; Lamkaddam, Houssni; Lee, Chuan P.; Lehtipalo, Katrianne; Leiminger, Markus; Mai, Huajun; Manninen, Hanna E.; Marie, Guillaume; Marten, Ruby; Mentler, Bernhard; Molteni, Ugo; Nichman, Leonid; Nie, Wei; Ojdanic, Andrea; Onnela, Antti; Partoll, Eva; Petaejae, Tuukka; Pfeifer, Joschka; Philippov, Maxim; Quelever, Lauriane L. J.; Ranjithkumar, Ananth; Rissanen, Matti P.; Schallhart, Simon; Schobesberger, Siegfried; Schuchmann, Simone; Shen, Jiali; Sipilae, Mikko; Steiner, Gerhard; Stozhkov, Yuri; Tauber, Christian; Tham, Yee J.; Tome, Antonio R.; Vazquez-Pufleau, Miguel; Vogel, Alexander L.; Wagner, Robert; Wang, Mingyi; Wang, Dongyu S.; Wang, Yonghong; Weber, Stefan K.; Wu, Yusheng; Xiao, Mao; Yan, Chao; Ye, Penglin; Ye, Qing; Zauner-Wieczorek, Marcel; Zhou, Xueqin; Baltensperger, Urs; Dommen, Josef; Flagan, Richard C.; Hansel, Armin; Kulmala, Markku; Volkamer, Rainer; Winkler, Paul M.; Worsnop, Douglas R.; Donahue, Neil M.; Kirkby, Jasper; Curtius, Joachim
      Atmospheric Chemistry and Physics (2020), 20 (15), 9183-9207CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
      Highly oxygenated org. mols. (HOMs) contribute substantially to the formation and growth of atm. aerosol particles, which affect air quality, human health and Earth's climate. HOMs are formed by rapid, gas-phase autoxidn. of volatile org. compds. (VOCs) such as α-pinene, the most abundant monoterpene in the atm. Due to their abundance and low volatility, HOMs can play an important role in new-particle formation (NPF) and the early growth of atm. aerosols, even without any further assistance of other low-volatility compds. such as sulfuric acid. Both the autoxidn. reaction forming HOMs and their NPF rates are expected to be strongly dependent on temp. However, exptl. data on both effects are limited. Dedicated expts. were performed at the CLOUD (Cosmics Leaving OUtdoor Droplets) chamber at CERN to address this question. In this study, we show that a decrease in temp. (from +25 to -50 °C) results in a reduced HOM yield and reduced oxidn. state of the products, whereas the NPF rates (J1.7 nm) increase substantially. Measurements with two different chem. ionization mass spectrometers (using nitrate and protonated water as reagent ion, resp.) provide the mol. compn. of the gaseous oxidn. products, and a two-dimensional volatility basis set (2D VBS) model provides their volatility distribution. The HOM yield decreases with temp. from 6.2 % at 25 °C to 0.7 % at -50 °C. However, there is a strong redn. of the satn. vapor pressure of each oxidn. state as the temp. is reduced. Overall, the redn. in volatility with temp. leads to an increase in the nucleation rates by up to 3 orders of magnitude at -50 °C compared with 25 °C. In addn., the enhancement of the nucleation rates by ions decreases with decreasing temp., since the neutral mol. clusters have increased stability against evapn. The resulting data quantify how the interplay between the temp.-dependent oxidn. pathways and the assocd. vapor pressures affect biogenic NPF at the mol. level. Our measurements, therefore, improve our understanding of pure biogenic NPF for a wide range of tropospheric temps. and precursor concns.
      (b) Heinritzi, M.; Dada, L.; Simon, M.; Stolzenburg, D.; Wagner, A. C.; Fischer, L.; Ahonen, L. R.; Amanatidis, S.; Baalbaki, R.; Baccarini, A. Molecular understanding of the suppression of new-particle formation by isoprene. Atmos. Chem. Phys. 2020, 20, 11809– 11821,  DOI: 10.5194/acp-20-11809-2020
      7b
      Molecular understanding of the suppression of new-particle formation by isoprene
      Heinritzi, Martin; Dada, Lubna; Simon, Mario; Stolzenburg, Dominik; Wagner, Andrea C.; Fischer, Lukas; Ahonen, Lauri R.; Amanatidis, Stavros; Baalbaki, Rima; Baccarini, Andrea; Bauer, Paulus S.; Baumgartner, Bernhard; Bianchi, Federico; Brilke, Sophia; Chen, Dexian; Chiu, Randall; Dias, Antonio; Dommen, Josef; Duplissy, Jonathan; Finkenzeller, Henning; Frege, Carla; Fuchs, Claudia; Garmash, Olga; Gordon, Hamish; Granzin, Manuel; El Haddad, Imad; He, Xucheng; Helm, Johanna; Hofbauer, Victoria; Hoyle, Christopher R.; Kangasluoma, Juha; Keber, Timo; Kim, Changhyuk; Kuerten, Andreas; Lamkaddam, Houssni; Laurila, Tiia M.; Lampilahti, Janne; Lee, Chuan Ping; Lehtipalo, Katrianne; Leiminger, Markus; Mai, Huajun; Makhmutov, Vladimir; Manninen, Hanna Elina; Marten, Ruby; Mathot, Serge; Mauldin, Roy Lee; Mentler, Bernhard; Molteni, Ugo; Mueller, Tatjana; Nie, Wei; Nieminen, Tuomo; Onnela, Antti; Partol, Eva; Passananti, Monica; Petaejae, Tuukka; Pfeifer, Joschka; Pospisilova, Veronika; Quelever, Lauriane L. J.; Rissanen, Matti P.; Rose, Clemence; Schobesberger, Siegfried; Scholz, Wiebke; Scholze, Kay; Sipilae, Mikko; Steiner, Gerhard; Stozhkov, Yuri; Tauber, Christian; Tham, Yee Jun; Vazquez-Pufleau, Miguel; Virtanen, Annele; Vogel, Alexander L.; Volkamer, Rainer; Wagner, Robert; Wang, Mingyi; Weitz, Lena; Wimmer, Daniela; Xiao, Mao; Yan, Chao; Ye, Penglin; Zha, Qiaozhi; Zhou, Xueqin; Amorim, Antonio; Baltensperger, Urs; Hanse, Armin; Kulmala, Markku; Tome, Antonio; Winkler, Paul M.; Worsnop, Douglas R.; Donahue, Neil M.; Kirkby, Jasper; Curtius, Joachim
      Atmospheric Chemistry and Physics (2020), 20 (20), 11809-11821CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
      Nucleation of atm. vapors produces more than half of global cloud condensation nuclei and so has an important influence on climate. Recent studies show that monoterpene (C10H16) oxidn. yields highly oxygenated products that can nucleate with or without sulfuric acid. Monoterpenes are emitted mainly by trees, frequently together with isoprene (C5H8), which has the highest global emission of all org. vapors. Previous studies have shown that isoprene suppresses new-particle formation from monoterpenes, but the cause of this suppression is under debate. Here, in expts. performed under atm. conditions in the CERN CLOUD chamber, we show that isoprene reduces the yield of highly oxygenated dimers with 19 or 20 carbon atoms which drive particle nucleation and early growth while increasing the prodn. of dimers with 14 or 15 carbon atoms. The dimers (termed C20 and C15, resp.) are produced by termination reactions between pairs of peroxy radicals (RO2·) arising from monoterpenes or isoprene. Compared with pure monoterpene conditions, isoprene reduces nucleation rates at 1.7 nm (depending on the isoprene / monoterpene ratio) and approx. halves particle growth rates between 1.3 and 3.2 nm. However, above 3.2 nm, C15 dimers contribute to secondary org. aerosol, and the growth rates are unaffected by isoprene. We further show that increased hydroxyl radical (OH·) reduces particle formation in our chem. system rather than enhances it as previously proposed, since it increases isoprene-derived RO2· radicals that reduce C20 formation. RO2· termination emerges as the crit. step that dets. the highly oxygenated org. mol. (HOM) distribution and the corresponding nucleation capability. Species that reduce the C20 yield, such as NO, HO2 and as we show isoprene, can thus effectively reduce biogenic nucleation and early growth. Therefore the formation rate of org. aerosol in a particular region of the atm. under study will vary according to the precise ambient conditions.
      (c) Ye, Q.; Wang, M.; Hofbauer, V.; Stolzenburg, D.; Chen, D.; Schervish, M.; Vogel, A.; Mauldin, R. L.; Baalbaki, R.; Brilke, S. Molecular Composition and Volatility of Nucleated Particles from α-Pinene Oxidation between −50 °C and +25 °C. Environ. Sci. Technol. 2019, 53, 12357– 12365,  DOI: 10.1021/acs.est.9b03265
      7c
      Molecular Composition and Volatility of Nucleated Particles from α-Pinene Oxidation between -50 °C and +25 °C
      Ye, Qing; Wang, Mingyi; Hofbauer, Victoria; Stolzenburg, Dominik; Chen, Dexian; Schervish, Meredith; Vogel, Alexander; Mauldin, Roy L.; Baalbaki, Rima; Brilke, Sophia; Dada, Lubna; Dias, Antonio; Duplissy, Jonathan; El Haddad, Imad; Finkenzeller, Henning; Fischer, Lukas; He, Xucheng; Kim, Changhyuk; Kurten, Andreas; Lamkaddam, Houssni; Lee, Chuan Ping; Lehtipalo, Katrianne; Leiminger, Markus; Manninen, Hanna E.; Marten, Ruby; Mentler, Bernhard; Partoll, Eva; Petaja, Tuukka; Rissanen, Matti; Schobesberger, Siegfried; Schuchmann, Simone; Simon, Mario; Tham, Yee Jun; Vazquez-Pufleau, Miguel; Wagner, Andrea C.; Wang, Yonghong; Wu, Yusheng; Xiao, Mao; Baltensperger, Urs; Curtius, Joachim; Flagan, Richard; Kirkby, Jasper; Kulmala, Markku; Volkamer, Rainer; Winkler, Paul M.; Worsnop, Douglas; Donahue, Neil M.
      Environmental Science & Technology (2019), 53 (21), 12357-12365CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      We use a real-time temp.-programmed desorption chem.-ionization mass spectrometer (FIGAERO-CIMS) to measure particle-phase compn. and volatility of nucleated particles, studying pure α-pinene oxidn. over a wide temp. range (-50° to +25°) in the CLOUD chamber at CERN. Highly-oxygenated org. mols. are much more abundant in particles formed at higher temps., shifting the compds. towards higher O:C and lower intrinsic (300 K) volatility. We find that pure biogenic nucleation and growth depends only weakly on temp. This is because the pos. temp. dependence of degree of oxidn. (and polarity) and the neg. temp. dependence of volatility counteract each other. Unlike prior work that relied on estd. volatility, we directly measure volatility via calibrated temp. programmed desorption. The particle-phase measurements are consistent with gas-phase results and indicate that during new-particle formation from α-pinene oxidn., gas-phase chem. directly dets. the properties of materials in the condensed phase. We now have consistency between measured gas-phase product concns., product volatility, measured and modeled growth rates, and the particle compn. over most temps. found in the troposphere.
      (d) Frege, C.; Ortega, I. K.; Rissanen, M. P.; Praplan, A. P.; Steiner, G.; Heinritzi, M.; Ahonen, L.; Amorim, A.; Bernhammer, A.-K.; Bianchi, F. Influence of temperature on the molecular composition of ions and charged clusters during pure biogenic nucleation. Atmos. Chem. Phys. 2018, 18, 65– 79,  DOI: 10.5194/acp-18-65-2018
      7d
      Influence of temperature on the molecular composition of ions and charged clusters during pure biogenic nucleation
      Frege, Carla; Ortega, Ismael K.; Rissanen, Matti P.; Praplan, Arnaud P.; Steiner, Gerhard; Heinritzi, Martin; Ahonen, Lauri; Amorim, Antonio; Bernhammer, Anne-Kathrin; Bianchi, Federico; Brilke, Sophia; Breitenlechner, Martin; Dada, Lubna; Dias, Antonio; Duplissy, Jonathan; Ehrhart, Sebastian; El-Haddad, Imad; Fischer, Lukas; Fuchs, Claudia; Garmash, Olga; Gonin, Marc; Hansel, Armin; Hoyle, Christopher R.; Jokinen, Tuija; Junninen, Heikki; Kirkby, Jasper; Kurten, Andreas; Lehtipalo, Katrianne; Leiminger, Markus; Mauldin, Roy Lee; Molteni, Ugo; Nichman, Leonid; Petaja, Tuukka; Sarnela, Nina; Schobesberger, Siegfried; Simon, Mario; Sipila, Mikko; Stolzenburg, Dominik; Tome, Antonio; Vogel, Alexander L.; Wagner, Andrea C.; Wagner, Robert; Xiao, Mao; Yan, Chao; Ye, Penglin; Curtius, Joachim; Donahue, Neil M.; Flagan, Richard C.; Kulmala, Markku; Worsnop, Douglas R.; Winkler, Paul M.; Dommen, Josef; Baltensperger, Urs
      Atmospheric Chemistry and Physics (2018), 18 (1), 65-79CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
      It was recently shown by the CERN CLOUD expt. that biogenic highly oxygenated mols. (HOMs) form particles under atm. conditions in the absence of sulfuric acid, where ions enhance the nucleation rate by 1-2 orders of magnitude. The biogenic HOMs were produced from ozonolysis of α-pinene at 5 °C. Here, we extend this study to compare the mol. compn. of pos. and neg. HOM clusters measured with atm. pressure interface time-of-flight mass spectrometers (APi-TOFs), at three different temps. (25, 5 and -25 °C). Most neg. HOM clusters include a nitrate (NO3- ) ion, and the spectra are similar to those seen in the nighttime boreal forest. On the other hand, most pos. HOM clusters include an ammonium (NH4+) ion, and the spectra are characterized by mass bands that differ in their mol. wt. by ∼20 C atoms, corresponding to HOM dimers. At lower temps. the av. oxygen to carbon (O : C) ratio of the HOM clusters decreases for both polarities, reflecting an overall redn. of HOM formation with decreasing temp. This indicates a decrease in the rate of autoxidn. with temp. due to a rather high activation energy as has previously been detd. by quantum chem. calcns. Furthermore, at the lowest temp. (∼25 °C), the presence of C30 clusters shows that HOM monomers start to contribute to the nucleation of pos. clusters. These exptl. findings are supported by quantum chem. calcns. of the binding energies of representative neutral and charged clusters.
      (e) Lehtipalo, K.; Yan, C.; Dada, L.; Bianchi, F.; Xiao, M.; Wagner, R.; Stolzenburg, D.; Ahonen, L. R.; Amorim, A.; Baccarini, A. Multicomponent new particle formation from sulfuric acid, ammonia, and biogenic vapors. Sci. Adv. 2018, 4, eaau5363  DOI: 10.1126/sciadv.aau5363
      There is no corresponding record for this reference.
    8. 8
      (a) Dommen, J.; Metzger, A.; Duplissy, J.; Kalberer, M.; Alfarra, M. R.; Gascho, A.; Weingartner, E.; Prevot, A. S. H.; Verheggen, B.; Baltensperger, U. Laboratory observation of oligomers in the aerosol from isoprene/NOx photooxidation. Geophys. Res. Lett. 2006, 33, L13805,  DOI: 10.1029/2006gl026523
      8a
      Laboratory observation of oligomers in the aerosol from isoprene/NOx photooxidation
      Dommen, J.; Metzger, A.; Duplissy, J.; Kalberer, M.; Alfarra, M. R.; Gascho, A.; Weingartner, E.; Prevot, A. S. H.; Verheggen, B.; Baltensperger, U.
      Geophysical Research Letters (2006), 33 (13), L13805/1-L13805/5CODEN: GPRLAJ; ISSN:0094-8276. (American Geophysical Union)
      Compds. assigned to be oxidn. products of isoprene (2-methyl-1,3-butadiene) have recently been obsd. in ambient aerosols, suggesting that isoprene might play an important role in secondary org. aerosol (SOA) formation due to its large global source strength. SOA yields from photooxidn. of isoprene and NOx in a chamber agree fairly well with previous data. Matrix assisted laser desorption/ionization mass spectrometry showed the formation of high mol. wt. compds. over the course of 15-h expts. Concurrently, the volatility of the SOA decreased markedly as obsd. by a tandem differential mobility analyzer. The vol. fraction remaining of SOA at 150°C increased steadily from 5 to 25% during the same expts. These observations are attributed to oligomerization reactions occurring in the aerosol phase. Under dry conditions a lower volatility was obsd.
      (b) Kalberer, M.; Paulsen, D.; Sax, M.; Steinbacher, M.; Dommen, J.; Prevot, A. S. H.; Fisseha, R.; Weingartner, E.; Frankevich, V.; Zenobi, R. Identification of Polymers as Major Components of Atmospheric Organic Aerosols. Science 2004, 303, 1659– 1662,  DOI: 10.1126/science.1092185
      8b
      Identification of Polymers as Major Components of Atmospheric Organic Aerosols
      Kalberer, M.; Paulsen, D.; Sax, M.; Steinbacher, M.; Dommen, J.; Prevot, A. S. H.; Fisseha, R.; Weingartner, E.; Frankevich, V.; Zenobi, R.; Baltensperger, U.
      Science (Washington, DC, United States) (2004), 303 (5664), 1659-1662CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
      The results from photooxidn. of arom. compds. in a reaction chamber show that a substantial fraction of the org. aerosol mass is composed of polymers. This polymn. results from reactions of carbonyls and their hydrates. After aging for more than 20 h, about 50% of the particle mass consists of polymers with a mol. mass up to 1000 daltons. This results in a lower volatility of this secondary org. aerosol and a higher aerosol yield than a model using vapor pressures of individual org. species would predict.
      (c) Laskin, A.; Laskin, J.; Nizkorodov, S. A. Mass spectrometric approaches for chemical characterisation of atmospheric aerosols: critical review of the most recent advances. Environ. Chem. 2012, 9, 163– 189,  DOI: 10.1071/en12052
      8c
      Mass spectrometric approaches for chemical characterisation of atmospheric aerosols: critical review of the most recent advances
      Laskin, Alexander; Laskin, Julia; Nizkorodov, Sergey A.
      Environmental Chemistry (2012), 9 (3), 163-189CODEN: ECNHAA; ISSN:1449-8979. (CSIRO Publishing)
      A review. Environmental contextAtmospheric aerosols have profound effects on the environment through several physicochem. processes, such as absorption and scattering of sunlight, heterogeneous gas-particle reactions and adverse effects on the respiratory and cardiovascular systems. Understanding aerosol atm. chem. and its environmental impact requires comprehensive characterization of the phys. and chem. properties of particles. Results from mass spectrometry provide important new insights into the origin of atm. aerosols, the evolution of their physicochem. properties, their reactivity and their effect on the environment. This manuscript presents an overview of the most recent instrument developments for the field and lab. applications of mass spectrometry (MS) to investigate the chem. and physics of atm. aerosols. A range of MS instruments, employing different sample introduction methods, ionisation and mass detection techniques are used both for online' and offline' characterization of aerosols. Online MS techniques enable detection of individual particles with simultaneous measurement of particle size distributions and aerodynamic characteristics and are ideally suited for field studies that require high temporal resoln. Offline MS techniques provide a means for detailed mol.-level anal. of aerosol samples, which is essential to gain fundamental knowledge regarding aerosol chem., mechanisms of particle formation and atm. aging. Combined, complementary MS techniques provide comprehensive information on the chem. compn., size, morphol. and phase of aerosols - data of key importance for evaluating hygroscopic and optical properties of particles, their health effects, understanding their origins and atm. evolution. Over the last few years, developments and applications of MS techniques in aerosol research have expanded remarkably as evident by skyrocketing publication statistics. The goal of this review is to present the most recent developments in the field of aerosol mass spectrometry for the time period of late 2010 to early 2012, which have not been conveyed in previous reviews.
      (d) Walser, M. L.; Desyaterik, Y.; Laskin, J.; Laskin, A.; Nizkorodov, S. A. High-resolution mass spectrometric analysis of secondary organic aerosol produced by ozonation of limonene. Phys. Chem. Chem. Phys. 2008, 10, 1009– 1022,  DOI: 10.1039/B712620D
      8d
      High-resolution mass spectrometric analysis of secondary organic aerosol produced by ozonation of limonene
      Walser, Maggie L.; Desyaterik, Yury; Laskin, Julia; Laskin, Alexander; Nizkorodov, Sergey A.
      Physical Chemistry Chemical Physics (2008), 10 (7), 1009-1022CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
      The chem. compn. of secondary org. aerosols (SOA) formed from O3-initiated oxidn. of limonene was characterized by high-resoln. electro-spray ionization/mass spectrometry in pos. and neg. ion modes. Mass spectra showed a large no. of monomeric (m/z <300) and oligomeric (m/z >300) condensed oxidn. products. A combination of high resolving power (m/Δm ∼60,000) and Kendrick mass defect anal. made it possible to unambiguously det. the mol. compn. of hundreds of individual compds. in SOA samples. Van Krevelen anal. showed SOA compds. were heavily oxidized, with av. O:C ratios of 0.43 and 0.50 detd. from pos. and neg. ion mode spectra, resp. A possible reaction mechanism for formation of first generation SOA mol. components is presented. This mechanism includes known isomerization and addn. reactions of carbonyl oxide intermediates generated during limonene ozonation. Also, it includes isomerization and decompn. pathways for alkoxy radicals resulting from unimol. decompn. of carbonyl oxides which were disregarded in previous studies. Isomerization reactions yielded numerous products with a progressively increasing no. of alc. and carbonyl groups; C-C bond scission reactions in alkoxy radicals shortened the C chain. Together these reactions yielded a large no. of isomeric products with broadly distributed masses. A qual. agreement was obsd. between the no. and degree of oxidn. of predicted and measured reaction products in the monomer product range.
      (e) Bateman, A. P.; Walser, M. L.; Desyaterik, Y.; Laskin, J.; Laskin, A.; Nizkorodov, S. A. The Effect of Solvent on the Analysis of Secondary Organic Aerosol Using Electrospray Ionization Mass Spectrometry. Environ. Sci. Technol. 2008, 42, 7341– 7346,  DOI: 10.1021/es801226w
      8e
      The Effect of Solvent on the Analysis of Secondary Organic Aerosol Using Electrospray Ionization Mass Spectrometry
      Bateman, Adam P.; Walser, Maggie L.; Desyaterik, Yury; Laskin, Julia; Laskin, Alexander; Nizkorodov, Sergey A.
      Environmental Science & Technology (2008), 42 (19), 7341-7346CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      This work examd. the effect of solvent on org. aerosol ext. anal. by electro-spray ionization/mass spectrometry (ESI/MS). Secondary org. aerosol (SOA) produced by ozonation of d-limonene and several org. mols. with functional groups typical for OA constituents, were extd. in methanol, d3-methanol, acetonitrile, and d3-acetonitrile to assess the extent and relative rates of reactions between analyte and solvent. High resoln. ESI-MS showed reactions of carbonyls with methanol produced significant amts. of hemiacetals and acetals on time scales of several minutes to several days; reaction rates increased in acidified soln. Carboxylic acid groups reacted with methanol forming esters. Acetonitrile exts. demonstrated no evidence of reactions with analyte mols., suggesting acetonitrile is the preferred solvent for SOA extn. Using solvent-analyte reactivity as a tool to improve characterization of functional groups in complex org. mixts. was demonstrated. Direct comparison between mass spectra of the same SOA samples extd. in methanol vs. acetonitrile estd. lower limits for relative fractions of carbonyls (≥42%) and carboxylic acids (≥55%) in d-limonene SOA.
    9. 9
      (a) Müller, M.; Piel, F.; Gutmann, R.; Sulzer, P.; Hartungen, E.; Wisthaler, A. A novel method for producing NH4+ reagent ions in the hollow cathode glow discharge ion source of PTR-MS instruments. Int. J. Mass Spectrom. 2020, 447, 116254,  DOI: 10.1016/j.ijms.2019.116254
      9a
      A novel method for producing NH+4 reagent ions in the hollow cathode glow discharge ion source of PTR-MS instruments
      Mueller, Markus; Piel, Felix; Gutmann, Rene; Sulzer, Philipp; Hartungen, Eugen; Wisthaler, Armin
      International Journal of Mass Spectrometry (2020), 447 (), 116254CODEN: IMSPF8; ISSN:1387-3806. (Elsevier B.V.)
      Proton-transfer-reaction mass spectrometry (PTR-MS) is seeing an increased use of NH+4 ions for the detection of amines and labile oxygenated org. compds. NH+4 ions are usually generated from ammonia or ammonium-contg. chems. We herein present a simple method for generating NH+4 reagent ions in the hollow cathode glow discharge ion source that nowadays most proton-transfer-reaction mass spectrometry (PTR-MS) instruments are equipped with. We show that NH+4 ions can be generated in high purity and yield by simply introducing a mixt. of water vapor and nitrogen in the ion source. We also show that rapid switching (~ 10 s loss of data) between the H3O+ and NH+4 operation modes is possible. Our new method can be easily implemented in most PTR-MS instruments that are currently in use, thus opening the possibility to easily operate the PTR-MS analyzer in the NH+4 chem. ionization mode.
      (b) Leglise, J.; Müller, M.; Piel, F.; Otto, T.; Wisthaler, A. Bulk Organic Aerosol Analysis by Proton-Transfer-Reaction Mass Spectrometry: An Improved Methodology for the Determination of Total Organic Mass, O:C and H:C Elemental Ratios, and the Average Molecular Formula. Anal. Chem. 2019, 91, 12619– 12624,  DOI: 10.1021/acs.analchem.9b02949
      9b
      Bulk Organic Aerosol Analysis by Proton-Transfer-Reaction Mass Spectrometry: An Improved Methodology for the Determination of Total Organic Mass, O:C and H:C Elemental Ratios, and the Average Molecular Formula
      Leglise, Joris; Muller, Markus; Piel, Felix; Otto, Tobias; Wisthaler, Armin
      Analytical Chemistry (Washington, DC, United States) (2019), 91 (20), 12619-12624CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)
      The authors recently showed (M. Muller, et al., 2017) how a proton-transfer-reaction mass spectrometry (PTR-MS) analyzer measured particulate org. matter in urban atmospheres using a chem. anal. of aerosol online (CHARON) inlet. Initial CHARON studies did not account for fragmentation of protonated analyte mols., which introduced a small but significant neg. bias in bulk org. aerosol parameters detn. This work examd. the ionic fragmentation of 26 oxidized org. compds. typically occurring in atm. particles. This allowed the authors to derive a correction algorithm to det. the bulk org. mass concn. (mOA), the bulk-av. H:C ratio ([H:C]bulk), the bulk-av. O:C ratio ([O:C]bulk), and the bulk-av. mol. formula, MFbulk. The correction algorithm was validated against AMS data using two sets of published data. The authors then detd. MFbulk of particles generated from an α-pinene/O3 reaction, and compared and discussed results in relation to the literature.
      (c) Eichler, P.; Müller, M.; D’Anna, B.; Wisthaler, A. A novel inlet system for online chemical analysis of semi-volatile submicron particulate matter. Atmos. Meas. Tech. 2015, 8, 1353– 1360,  DOI: 10.5194/amt-8-1353-2015
      9c
      A novel inlet system for online chemical analysis of semi-volatile submicron particulate matter
      Eichler, P.; Mueller, M.; D'Anna, B.; Wisthaler, A.
      Atmospheric Measurement Techniques (2015), 8 (3), 1353-1360CODEN: AMTTC2; ISSN:1867-8548. (Copernicus Publications)
      We herein present a novel modular inlet system designed to be coupled to low-pressure gas analyzers for online chem. characterization of semi-volatile submicron particles. The "chem. anal. of aerosol online" (CHARON) inlet consists of a gas-phase denuder for stripping off gasphase analytes, an aerodynamic lens for particle collimation combined with an inertial sampler for the particle-enriched flow and a thermodesorption unit for particle volatilization prior to chem. anal. The denuder was measured to remove gas-phase orgs. with an efficiency > 99.999% and to transmit particles in the 100-750 nm size range with a 75-90% efficiency. The measured av. particle enrichment factor in the subsampling flow from the aerodynamic lens was 25.6, which is a factor of 3 lower than the calcd. theor. optimum. We coupled the CHARON inlet to a proton-transferreaction time-of-flight mass spectrometer (PTR-ToF-MS) which quant. detects most org. analytes and ammonia. The combined CHARON-PTR-ToF-MS setup is thus capable of measuring both the org. and the ammonium fraction in submicron particles in real time. Individual org. compds. can be detected down to levels of 10-20 ngm-3 Two proof-of-principle studies were carried out for demonstrating the anal. power of this new instrumental setup: (i) oxygenated orgs. and their partitioning between the gas and the particulate phase were obsd. from the reaction of limonene with ozone and (ii) nicotine was measured in cigarette smoke particles demonstrating that selected org. target compds. can be detected in submicron particles in real time.
      (d) Huang, W.; Saathoff, H.; Shen, X.; Ramisetty, R.; Leisner, T.; Mohr, C. Chemical Characterization of Highly Functionalized Organonitrates Contributing to Night-Time Organic Aerosol Mass Loadings and Particle Growth. Environ. Sci. Technol. 2019, 53, 1165– 1174,  DOI: 10.1021/acs.est.8b05826
      9d
      Chemical Characterization of Highly Functionalized Organonitrates Contributing to Night-Time Organic Aerosol Mass Loadings and Particle Growth
      Huang, Wei; Saathoff, Harald; Shen, Xiaoli; Ramisetty, Ramakrishna; Leisner, Thomas; Mohr, Claudia
      Environmental Science & Technology (2019), 53 (3), 1165-1174CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      Reactions of volatile org. compds. (VOC) with NO3 radicals and of reactive intermediates of oxidized VOC with NOx can lead to the formation of highly functionalized organonitrates (ON). We present quant. and chem. information on ON contributing to high night-time org. aerosol (OA) mass concns. measured during July-August 2016 in a rural area in southwest Germany. A filter inlet for gases and aerosols coupled to a high-resoln. time-of-flight chem. ionization mass spectrometer (FIGAERO-HR-ToF-CIMS) was used to analyze the mol. compn. of ON in both the gas and particle phase. We find larger contributions of ON to OA mass during the night. Identified ON are highly functionalized, with 4 to 12 oxygen atoms. The diel patterns of ON compds. with 5, 7, 10, or 15 carbon atoms per mol. vary, indicating a corresponding behavior of their potential precursor VOC. The temporal behavior of ON after sunset correlates with that of the no. concn. of ultrafine particles, indicating a potential role of ON in night-time new particle formation (NPF) regularly obsd. at this location. We est. an ON contribution of 18-25% to the mass increase of newly formed particles after sunset. Our study provides insights into the chem. compn. of highly functionalized ON in the rural atm. and the role of anthropogenic emissions for night-time SOA formation in an area where biogenic VOC emissions dominate.
      (e) Mohr, C.; Lopez-Hilfiker, F. D.; Yli-Juuti, T.; Heitto, A.; Lutz, A.; Hallquist, M.; D’Ambro, E. L.; Rissanen, M. P.; Hao, L.; Schobesberger, S. Ambient observations of dimers from terpene oxidation in the gas phase: Implications for new particle formation and growth. Geophys. Res. Lett. 2017, 44, 2958– 2966,  DOI: 10.1002/2017gl072718
      9e
      Ambient observations of dimers from terpene oxidation in the gas phase: Implications for new particle formation and growth
      Mohr, Claudia; Lopez-Hilfiker, Felipe D.; Yli-Juuti, Taina; Heitto, Arto; Lutz, Anna; Hallquist, Mattias; D'Ambro, Emma L.; Rissanen, Matti P.; Hao, Liqing; Schobesberger, Siegfried; Kulmala, Markku; Mauldin, Roy L., III; Makkonen, Ulla; Sipilae, Mikko; Petaejae, Tuukka; Thornton, Joel A.
      Geophysical Research Letters (2017), 44 (6), 2958-2966CODEN: GPRLAJ; ISSN:1944-8007. (Wiley-Blackwell)
      We present ambient observations of dimeric monoterpene oxidn. products (C16-20HyO6-9) in gas and particle phases in the boreal forest in Finland in spring 2013 and 2014, detected with a chem. ionization mass spectrometer with a filter inlet for gases and aerosols employing acetate and iodide as reagent ions. These are among the first online dual-phase observations of such dimers in the atm. Estd. satn. concns. of 10-15 to 10-6 μg m-3 (based on obsd. thermal desorptions and group-contribution methods) and measured gas-phase concns. of 10-3 to 10-2 μg m-3 (∼106-107 mols. cm-3) corroborate a gas-phase formation mechanism. Regular new particle formation (NPF) events allowed insights into the potential role dimers may play for atm. NPF and growth. The observationally constrained Model for Acid-Base chem. in NAnoparticle Growth indicates a contribution of ∼5% to early stage particle growth from the ∼60 gaseous dimer compds.
    10. 10
      Wu, C.; Bell, D. M.; Graham, E. L.; Haslett, S.; Riipinen, I.; Baltensperger, U.; Bertrand, A.; Giannoukos, S.; Schoonbaert, J.; El Haddad, I. Photolytically induced changes in composition and volatility of biogenic secondary organic aerosol from nitrate radical oxidation during night-to-day transition. Atmos. Chem. Phys. 2021, 21, 14907– 14925,  DOI: 10.5194/acp-21-14907-2021
      10
      Photolytically induced changes in composition and volatility of biogenic secondary organic aerosol from nitrate radical oxidation during night-to-day transition
      Wu, Cheng; Bell, David M.; Graham, Emelie L.; Haslett, Sophie; Riipinen, Ilona; Baltensperger, Urs; Bertrand, Amelie; Giannoukos, Stamatios; Schoonbaert, Janne; El Haddad, Imad; Prevot, Andre S. H.; Huang, Wei; Mohr, Claudia
      Atmospheric Chemistry and Physics (2021), 21 (19), 14907-14925CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
      Night-time reactions of biogenic volatile org. compds. (BVOCs) and nitrate radicals (NO3) can lead to the formation of NO3-initiated biogenic secondary org. aerosol (BSOANO3). Here, we study the impacts of light exposure on the chem. compn. and volatility of BSOANO3 formed in the dark from three precursors (isoprene, α-pinene, and β-caryophyllene) in atm. simulation chamber expts. Our study represents BSOANO3 formation conditions where reactions between peroxy radicals (RO2 + RO2) and between RO2 and NO3 are favored. The emphasis here is on the identification of particle-phase organonitrates (ONs) formed in the dark and their changes during photolytic ageing on timescales of ~ 1 h. The chem. compn. of particle-phase compds. was measured with a chem. ionization mass spectrometer with a filter inlet for gases and aerosols (FIGAERO-CIMS) and an extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF). Volatility information on BSOANO3 was derived from FIGAERO-CIMS desorption profiles (thermograms) and a volatility tandem differential mobility analyzer (VTDMA). During photolytic ageing, there was a relatively small change in mass due to evapn. (< 5% for the isoprene and α-pinene BSOANO3, and 12% for the β-caryophyllene BSOANO3), but we obsd. significant changes in the chem. compn. of the BSOANO3. Overall, 48%, 44%, and 60% of the resp. total signal for the isoprene, α-pinene, and β-caryophyllene BSOANO3 was sensitive to photolytic ageing and exhibited decay. The photolabile compds. include both monomers and oligomers. Oligomers can decomp. into their monomer units through photolysis of the bonds (e.g. likely O-O) between them. Fragmentation of both oligomers and monomers also happened at other positions, causing the formation of compds. with shorter carbon skeletons. The cleavage of the nitrate functional group from the carbon chain was likely not a main degrdn. pathway in our expts. In addn., photolytic degrdn. of compds. changes their volatility and can lead to evapn. We use different methods to assess bulk volatilities and discuss their changes during both dark ageing and photolysis in the context of the chem. changes that we obsd. We also reveal large uncertainties in satn. vapor pressure estd. from parameterizations for the ON oligomers with multiple nitrate groups. Overall, our results suggest that photolysis causes photodegrdn. of a substantial fraction of BSOANO3, changes both the chem. compn. and the bulk volatility of the particles, and might be a potentially important loss pathway of BSOANO3 during the night-to-day transition.
    11. 11
      Lopez-Hilfiker, F. D.; Pospisilova, V.; Huang, W.; Kalberer, M.; Mohr, C.; Stefenelli, G.; Thornton, J. A.; Baltensperger, U.; Prevot, A. S. H.; Slowik, J. G. An extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF) for online measurement of atmospheric aerosol particles. Atmos. Meas. Tech. 2019, 12, 4867– 4886,  DOI: 10.5194/amt-12-4867-2019
      11
      An extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF) for online measurement of atmospheric aerosol particles
      Lopez-Hilfiker, Felipe D.; Pospisilova, Veronika; Huang, Wei; Kalberer, Markus; Mohr, Claudia; Stefenelli, Giulia; Thornton, Joel A.; Baltensperger, Urs; Prevot, Andre S. H.; Slowik, Jay G.
      Atmospheric Measurement Techniques (2019), 12 (9), 4867-4886CODEN: AMTTC2; ISSN:1867-8548. (Copernicus Publications)
      Real-time, online measurements of atm. org. aerosol (OA) compn. are an essential tool for detg. the emissions sources and physicochem. processes governing aerosol effects on climate and health. Aerosol particles are continuously sampled into the EESI-TOF, where they intersect a spray of charged droplets generated by a conventional electrospray probe. Sol. components are extd. and then ionized as the droplets are evapd. The EESI-TOF achieves a linear response to mass, with detection limits on the order of 1 to 10 ng m-3 in 5 s for typical atmospherically relevant compds. In contrast to conventional electrospray systems, the EESI-TOF response is not significantly affected by a changing OA matrix for the systems investigated. Although the relative sensitivities to a variety of com. available org. stds. vary by more than a factor of 30, the bulk sensitivity to secondary org. aerosol generated from individual precursor gases varies by only a factor of 15. Further, the ratio of compd.-by-compd. sensitivities between the EESI-TOF and an iodide adduct FIGAERO-I-CIMS varies by only ±50%, suggesting that EESI-TOF mass spectra indeed reflect the actual distribution of detectable compds. in the particle phase. Successful deployments of the EESI-TOF for lab. environmental chamber measurements, ground-based ambient sampling, and proof-of-concept measurements aboard a research aircraft highlight the versatility and potential of the EESI-TOF system.
    12. 12
      Lee, C. P.; Surdu, M.; Bell, D. M.; Lamkaddam, H.; Wang, M.; Ataei, F.; Hofbauer, V.; Lopez, B.; Donahue, N. M.; Dommen, J. Effects of Aerosol Size and Coating Thickness on the Molecular Detection using Extractive Electrospray Ionization. Atmos. Meas. Tech. 2021, 14, 5913– 5923,  DOI: 10.5194/amt-14-5913-2021
      12
      Effects of aerosol size and coating thickness on the molecular detection using extractive electrospray ionization
      Lee, Chuan Ping; Surdu, Mihnea; Bell, David M.; Lamkaddam, Houssni; Wang, Mingyi; Ataei, Farnoush; Hofbauer, Victoria; Lopez, Brandon; Donahue, Neil M.; Dommen, Josef; Prevot, Andre S. H.; Slowik, Jay G.; Wang, Dongyu; Baltensperger, Urs; El Haddad, Imad
      Atmospheric Measurement Techniques (2021), 14 (9), 5913-5923CODEN: AMTTC2; ISSN:1867-8548. (Copernicus Publications)
      Extractive electrospray ionization (EESI) has been a well-known technique for high-throughput online mol. characterization of chem. reaction products and intermediates, detection of native biomols., in vivo metabolomics, and environmental monitoring with negligible thermal and ionization-induced fragmentation for over two decades. However, the EESI extn. mechanism remains uncertain. Here, we examd. the analyte extn. mechanism by assessing the influence of particle size and coating thickness on the detection of the mols. therein. We also found that the EESI sensitivity exhibited a strong size dependence, with an increase in sensitivity by 1-3 orders of magnitude as particle size decreased from 300 to 30 nm. This dependence varied with the electrospray (ES) droplet size, the particle size and the residence time for coagulation in the EESI inlet, suggesting that the EESI sensitivity was influenced by the coagulation coeff. between particles and ES droplets. Overall, our results indicate that, in the EESI, particles are fully extd. by the ES droplets regardless of the chem. compn., when they are collected by the ES droplets. However, their coalescence is not complete and depends strongly on their size. This size dependence is esp. relevant when EESI is used to probe size-varying particles as is the case in aerosol formation and growth studies with size ranges below 100 nm.
    13. 13
      Pospisilova, V.; Bell, D. M.; Lamkaddam, H.; Bertrand, A.; Wang, L.; Bhattu, D.; Zhou, X.; Dommen, J.; Prevot, A. S. H.; Baltensperger, U. Photodegradation of α-Pinene Secondary Organic Aerosol Dominated by Moderately Oxidized Molecules. Environ. Sci. Technol. 2021, 55, 6936– 6943,  DOI: 10.1021/acs.est.0c06752
      13
      Photodegradation of α-pinene secondary organic aerosol dominated by moderately oxidized molecules
      Pospisilova, Veronika; Bell, David M.; Lamkaddam, Houssni; Bertrand, Amelie; Wang, Liwei; Bhattu, Deepika; Zhou, Xueqin; Dommen, Josef; Prevot, Andre S. H.; Baltensperger, Urs; El Haddad, Imad; Slowik, Jay G.
      Environmental Science & Technology (2021), 55 (10), 6936-6943CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      Atm. secondary org. aerosol (SOA) undergoes chem. and phys. changes when exposed to UV radiation, affecting the atm. lifetime of the involved mols. However, these photolytic processes remain poorly constrained. Here, we present a study aimed at characterizing, at a mol. level and in real time, the chem. compn. of α-pinene SOA exposed to UV-A light at 50% relative humidity in an atm. simulation chamber. Significant SOA mass loss is obsd. at high loadings (~ 100μg m-3), whereas the effect is less prevalent at lower loadings (~ 20μg m-3). For the vast majority of mols. measured by the extractive electrospray time-of-flight mass spectrometer, there is a fraction that is photoactive and decays when exposed to UV-A radiation and a fraction that appears photorecalcitrant. The mols. that are most photoactive contain between 4 and 6 oxygen atoms, while the more highly oxygenated compds. and dimers do not exhibit significant decay. Overall, photolysis results in a redn. of the volatility of SOA, which cannot be explained by simple evaporative losses but requires either a change in volatility related to changes in functional groups or a change in phys. parameters (i.e., viscosity).
    14. 14
      Surdu, M.; Pospisilova, V.; Xiao, M.; Wang, M.; Mentler, B.; Simon, M.; Stolzenburg, D.; Hoyle, C. R.; Bell, D. M.; Lee, C. P. Molecular characterization of ultrafine particles using extractive electrospray time-of-flight mass spectrometry. Environ. Sci.: Atmos. 2021, 1, 434– 448,  DOI: 10.1039/D1EA00050K
      14
      Molecular characterization of ultrafine particles using extractive electrospray time-of-flight mass spectrometry
      Surdu, Mihnea; Pospisilova, Veronika; Xiao, Mao; Wang, Mingyi; Mentler, Bernhard; Simon, Mario; Stolzenburg, Dominik; Hoyle, Christopher R.; Bell, David M.; Lee, Chuan Ping; Lamkaddam, Houssni; Lopez-Hilfiker, Felipe; Ahonen, Lauri R.; Amorim, Antonio; Baccarini, Andrea; Chen, Dexian; Dada, Lubna; Duplissy, Jonathan; Finkenzeller, Henning; He, Xu-Cheng; Hofbauer, Victoria; Kim, Changhyuk; Kurten, Andreas; Kvashnin, Aleksandr; Lehtipalo, Katrianne; Makhmutov, Vladimir; Molteni, Ugo; Nie, Wei; Onnela, Antti; Petaja, Tuukka; Quelever, Lauriane L. J.; Tauber, Christian; Tome, Antonio; Wagner, Robert; Yan, Chao; Prevot, Andre S. H.; Dommen, Josef; Donahue, Neil M.; Hansel, Armin; Curtius, Joachim; Winkler, Paul M.; Kulmala, Markku; Volkamer, Rainer; Flagan, Richard C.; Kirkby, Jasper; Worsnop, Douglas R.; Slowik, Jay G.; Wang, Dongyu S.; Baltensperger, Urs; Haddad, Imad el
      Environmental Science: Atmospheres (2021), 1 (6), 434-448CODEN: ESANC9; ISSN:2634-3606. (Royal Society of Chemistry)
      Aerosol particles neg. affect human health while also having climatic relevance due to, for example, their ability to act as cloud condensation nuclei. Ultrafine particles (diam. Dp < 100 nm) typically comprise the largest fraction of the total no. concn., however, their chem. characterization is difficult because of their low mass. Using an extractive electrospray time-of-flight mass spectrometer (EESI-TOF), we characterize the mol. compn. of freshly nucleated particles from naphthalene and β-caryophyllene oxidn. products at the CLOUD chamber at CERN. We perform a detailed intercomparison of the org. aerosol chem. compn. measured by the EESI-TOF and an iodide adduct chem. ionization mass spectrometer equipped with a filter inlet for gases and aerosols (FIGAERO-I-CIMS). We also use an aerosol growth model based on the condensation of org. vapors to show that the chem. compn. measured by the EESI-TOF is consistent with the expected condensed oxidn. products. This agreement could be further improved by constraining the EESI-TOF compd.-specific sensitivity or considering condensed-phase processes. Our results show that the EESI-TOF can obtain the chem. compn. of particles as small as 20 nm in diam. with mass loadings as low as hundreds of ng m-3 in real time. This was until now difficult to achieve, as other online instruments are often limited by size cutoffs, ionization/thermal fragmentation and/or semi-continuous sampling. Using real-time simultaneous gas- and particle-phase data, we discuss the condensation of naphthalene oxidn. products on a mol. level.
    15. 15
      Patriarca, C.; Balderrama, A.; Može, M.; Sjöberg, P. J. R.; Bergquist, J.; Tranvik, L. J.; Hawkes, J. A. Investigating the Ionization of Dissolved Organic Matter by Electrospray. Anal. Chem. 2020, 92, 14210– 14218,  DOI: 10.1021/acs.analchem.0c03438
      15
      Investigating the ionization of dissolved organic matter by electrospray
      Patriarca, Claudia; Balderrama, Andrea; Moze, Martina; Sjoeberg, Per J. R.; Bergquist, Jonas; Tranvik, Lars J.; Hawkes, Jeffrey A.
      Analytical Chemistry (Washington, DC, United States) (2020), 92 (20), 14210-14218CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)
      Electrospray ionization (ESI) operating in the neg. mode coupled to high-resoln. mass spectrometry is the most popular technique for the characterization of dissolved org. matter (DOM). The vast mol. heterogeneity and the functional group diversity of this complex mixt. prevents the efficient ionization of the org. material by a single ionization source, so the presence of uncharacterized material is unavoidable. The extent of this poorly ionizable pool of carbon is unknown, is presumably variable between samples, and can only be assessed by the combination of anal. with a uniform detection method. Charged aerosol detection (CAD), whose response is proportional to the amt. of nonvolatile material and is independent from the physicochem. properties of the analytes, is a suitable candidate. In this study, a fulvic acid mixt. was fractionated and analyzed by high-pressure liq. chromatog.-mass spectrometry in order to investigate the polarity and size distributions of highly and poorly ionizable material in the sample. Addnl., DOM samples of terrestrial and marine origins were analyzed to evaluate the variability of these pools across the land-sea aquatic continuum. The relative response factor values indicated that highly ionizable components of aquatic DOM mixts. are more hydrophilic and have lower mol. wt. than poorly ionizable components. Addnl., a discrepancy between the samples of terrestrial and marine origins was found, indicating that marine samples are better represented by ESI than terrestrial samples, which have an abundant portion of hydrophobic poorly ionizable material.
    16. 16
      The pre-publication history for this paper can be accessed here: http://www.biomedcentral.com/1471-2466/14/31/prepub.
      There is no corresponding record for this reference.
      (a) Qi, L.; Chen, M.; Stefenelli, G.; Pospisilova, V.; Tong, Y.; Bertrand, A.; Hueglin, C.; Ge, X.; Baltensperger, U.; Prévôt, A. S. H. Organic aerosol source apportionment in Zurich using an extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF-MS) – Part 2: biomass burning influences in winter. Atmos. Chem. Phys. 2019, 19, 8037– 8062,  DOI: 10.5194/acp-19-8037-2019
      16a
      Organic aerosol source apportionment in Zurich using an extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF-MS) - Part 2: biomass burning influences in winter
      Qi, Lu; Chen, Mindong; Stefenelli, Giulia; Pospisilova, Veronika; Tong, Yandong; Bertrand, Amelie; Hueglin, Christoph; Ge, Xinlei; Baltensperger, Urs; Prevot, Andre S. H.; Slowik, Jay G.
      Atmospheric Chemistry and Physics (2019), 19 (12), 8037-8062CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
      Real-time, in situ mol. compn. measurements of the org. fraction of fine particulate matter (PM2.5) remain challenging, hindering a full understanding of the climate impacts and health effects of PM2.5. In particular, the thermal decompn. and ionization-induced fragmentation affecting current techniques has limited a detailed investigation of secondary org. aerosol (SOA), which typically dominates OA. Here we deploy a novel extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF-MS) during winter 2017 in downtown Zurich, Switzerland, which overcomes these limitations, together with an Aerodyne high-resoln. time-of-flight aerosol mass spectrometer (HR-TOF-AMS) and supporting instrumentation. Pos. matrix factorization (PMF) implemented within the Multilinear Engine (ME-2) program was applied to the EESI-TOF-MS data to quantify the primary and secondary contributions to OA. An 11-factor soln. was selected as the best representation of the data, including five primary and six secondary factors. Primary factors showed influence from cooking, cigarette smoke, biomass burning (two factors) and a special local unknown event occurred only during two nights. Secondary factors were affected by biomass burning (three factors, distinguished by temp. and/or wind direction), organonitrates, monoterpene oxidn., and undetd. regional processing, in particular the contributions of wood combustion.
      (b) Stefenelli, G.; Pospisilova, V.; Lopez-Hilfiker, F. D.; Daellenbach, K. R.; Hüglin, C.; Tong, Y.; Baltensperger, U.; Prévôt, A. S. H.; Slowik, J. G. Organic aerosol source apportionment in Zurich using an extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF-MS) – Part 1: Biogenic influences and day–night chemistry in summer. Atmos. Chem. Phys. 2019, 19, 14825– 14848,  DOI: 10.5194/acp-19-14825-2019
      16b
      Organic aerosol source apportionment in Zurich using an extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF-MS) - part 1: biogenic influences and day-night chemistry in summer
      Stefenelli, Giulia; Pospisilova, Veronika; Lopez-Hilfiker, Felipe D.; Daellenbach, Kaspar R.; Huglin, Christoph; Tong, Yandong; Baltensperger, Urs; Prevot, Andre S. H.; Slowik, Jay G.
      Atmospheric Chemistry and Physics (2019), 19 (23), 14825-14848CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
      Improving the understanding of the health and climate impacts of aerosols remains challenging and is restricted by the limitations of current measurement techniques. Detailed investigation of secondary org. aerosol (SOA), which is typically the dominating fraction of the org. aerosol (OA), requires instrumentation capable of real-time, in situ measurements of mol. compn. In this study, we present the first ambient measurements by a novel extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF-MS). The EESI-TOF-MS was deployed along with a high-resoln. time-of-flight aerosol mass spectrometer (HR-ToF-AMS) during summer 2016 at an urban location (Zurich, Switzerland). Pos. matrix factorization (PMF), implemented within the Multilinear Engine (ME-2), was applied to the data from both instruments to quantify the primary and secondary contributions to OA. From the EESI-TOF-MS anal., a six-factor soln. was selected as the most representative and interpretable soln. for the investigated dataset, including two primary and four secondary factors. The primary factors are dominated by cooking and cigarette smoke signatures while the secondary factors are discriminated according to their daytime (two factors) and night-time (two factors) chem. All four factors showed strong influence by biogenic emissions but exhibited significant day-night differences.
    17. 17
      Bell, D. M.; Wu, C.; Bertrand, A.; Graham, E.; Schoonbaert, J.; Giannoukos, S.; Baltensperger, U.; Prevot, A. S. H.; Riipinen, I.; El Haddad, I. Particle-phase processing of α-pinene NO3 secondary organic aerosol in the dark. Atmos. Chem. Phys. 2022, 22, 13167– 13182,  DOI: 10.5194/acp-22-13167-2022
      17
      Particle-phase processing of α-pinene NO3 secondary organic aerosol in the dark
      Bell, David M.; Wu, Cheng; Bertrand, Amelie; Graham, Emelie; Schoonbaert, Janne; Giannoukos, Stamatios; Baltensperger, Urs; Prevot, Andre S. H.; Riipinen, Ilona; El Haddad, Imad; Mohr, Claudia
      Atmospheric Chemistry and Physics (2022), 22 (19), 13167-13182CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
      The NO3 radical represents a significant night time oxidant which is present downstream of polluted environments. Existing studies have investigated the formation of secondary org. aerosol (SOA) from NO3 radicals, focusing on the yields, general compn., and hydrolysis of organonitrates; however, there is limited knowledge about how the compn. of NO3-derived SOA evolves as a result of particle-phase reactions. Here, SOA was formed from the reaction of α-pinene with NO3 radicals generated from N2O5, and the resulting SOA was aged in the dark. The initial compn. of NO3-derived α-pinene SOA was slightly dependent upon the concn. of N2O5 injected (excess of NO3 or excess of α-pinene) but was largely dominated by dimer dinitrates (C20H32N2O8-13). Oxidn. reactions (e.g., C20H32N2O8 → C20H32N2O9 → C20H32N2O10) accounted for 60 %-70 % of the particle-phase reactions obsd. Fragmentation reactions and dimer degrdn. pathways made up the remainder of the particle-phase processes occurring. The exact oxidant is not known, although suggestions are offered (e.g., N2O5, org. peroxides, or peroxynitrates). Hydrolysis of -ONO2 functional groups was not an important loss term during dark aging under the relative humidity conditions of our expts. (58 %-62 %), and changes in the bulk organonitrate compn. were likely driven by evapn. of highly nitrogenated mols. Overall, 25 %-30 % of the particle-phase compn. changes as a function of particle-phase reactions during dark aging, representing an important atm. aging pathway.
    18. 18
      Liu, X.; Day, D. A.; Krechmer, J. E.; Brown, W.; Peng, Z.; Ziemann, P. J.; Jimenez, J. L. Direct measurements of semi-volatile organic compound dynamics show near-unity mass accommodation coefficients for diverse aerosols. Commun. Chem. 2019, 2, 98,  DOI: 10.1038/s42004-019-0200-x
      There is no corresponding record for this reference.
    19. 19
      Rovelli, G.; Jacobs, M. I.; Willis, M. D.; Rapf, R. J.; Prophet, A. M.; Wilson, K. R. A critical analysis of electrospray techniques for the determination of accelerated rates and mechanisms of chemical reactions in droplets. Chem. Sci. 2020, 11, 13026– 13043,  DOI: 10.1039/D0SC04611F
      19
      A critical analysis of electrospray techniques for the determination of accelerated rates and mechanisms of chemical reactions in droplets
      Rovelli, Grazia; Jacobs, Michael I.; Willis, Megan D.; Rapf, Rebecca J.; Prophet, Alexander M.; Wilson, Kevin R.
      Chemical Science (2020), 11 (48), 13026-13043CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
      Electrospray and Electrosonic Spray Ionization Mass Spectrometry (ESI-MS and ESSI-MS) have been widely used to report evidence that many chem. reactions in micro- and nano-droplets are dramatically accelerated by factors of ~ 102 to 106 relative to macroscale bulk solns. Despite electrospray's relative simplicity to both generate and detect reaction products in charged droplets using mass spectrometry, substantial complexity exists in how the electrospray process itself impacts the interpretation of the mechanism of these obsd. accelerated rates. ESI and ESSI are both coupled multi-phase processes, in which analytes in small charged droplets are transferred and detected as gas-phase ions with a mass spectrometer. As such, quant. examn. is needed to evaluate the impact of multiple exptl. factors on the magnitude and mechanisms of reaction acceleration. These include: (1) evaporative concn. of reactants as a function of droplet size and initial concn., (2) competition from gas-phase chem. and reactions on exptl. surfaces, (3) differences in ionization efficiency and ion transmission and (4) droplet charge. We examine (1-4) using numerical models, new ESI/ESSI-MS exptl. data, and prior literature to assess the limitations of these approaches and the exptl. best practices required to robustly interpret acceleration factors in micro- and nano-droplets produced by ESI and ESSI.
    20. 20
      (a) Krieger, U. K.; Siegrist, F.; Marcolli, C.; Emanuelsson, E. U.; Gøbel, F. M.; Bilde, M.; Marsh, A.; Reid, J. P.; Huisman, A. J.; Riipinen, I. A reference data set for validating vapor pressure measurement techniques: homologous series of polyethylene glycols. Atmos. Meas. Tech. 2018, 11, 49– 63,  DOI: 10.5194/amt-11-49-2018
      There is no corresponding record for this reference.
      (b) Ylisirniö, A.; Barreira, L. M. F.; Pullinen, I.; Buchholz, A.; Jayne, J.; Krechmer, J. E.; Worsnop, D. R.; Virtanen, A.; Schobesberger, S. On the calibration of FIGAERO-ToF-CIMS: importance and impact of calibrant delivery for the particle-phase calibration. Atmos. Meas. Tech. 2021, 14, 355– 367,  DOI: 10.5194/amt-14-355-2021
      20b
      On the calibration of FIGAERO-ToF-CIMS: importance and impact of calibrant delivery for the particle-phase calibration
      Ylisirnio, Arttu; Barreira, Luis m. f.; Pullinen, Iida; Buchholz, Angela; Jayne, John; Krechmer, Jordan e.; Worsnop, Douglas r.; Virtanen, Annele; Schobesberger, Siegfried
      Atmospheric Measurement Techniques (2021), 14 (1), 355-367CODEN: AMTTC2; ISSN:1867-8548. (Copernicus Publications)
      The Filter Inlet for Gases and AEROsols (FIGAERO) coupled with a time-of-flight chem. ionization mass spectrometer (ToF-CIMS) enables online measurements of both gas-phase and particle-phase chem. constituents of ambient aerosols. When properly calibrated, the incorporated particle filter collection and subsequent thermal desorption enable the direct measurement of volatility of said constituents. Previously published volatility calibration results however differ from each other significantly. In this study we investigate the reason for this discrepancy. We found a major source of error in the widely used syringe deposition calibration method that can lead to an overestimation of satn. vapor pressures by several orders of magnitude. We propose a new method for volatility calibration by using atomized calibration compds. that more accurately captures the evapn. of chem. constituents from ambient aerosol particles. For example, we found a difference of ∼ 15°C in obsd. Tmax values between the atomizer method and syringe method using the lowest soln. concn. (0.003 g L-1). This difference translates into a difference of up to 3 orders of magnitude in satn. concn. C* space. We justify our claim with evapn. modeling and direct SEM imaging, while also presenting possible error sources of the atomizer method. We finally present how typical calibration parameters derived with both methods impact the volatility basis set (VBS) derived from measurements of secondary org. aerosols (SOAs).
    21. 21
      (a) Bell, D. M.; Imre, D.; T Martin, S.; Zelenyuk, A. The properties and behavior of α-pinene secondary organic aerosol particles exposed to ammonia under dry conditions. Phys. Chem. Chem. Phys. 2017, 19, 6497– 6507,  DOI: 10.1039/C6CP08839B
      21a
      The properties and behavior of α-pinene secondary organic aerosol particles exposed to ammonia under dry conditions
      Bell, David M.; Imre, Dan; T. Martin, Scot; Zelenyuk, Alla
      Physical Chemistry Chemical Physics (2017), 19 (9), 6497-6507CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
      Chem. transformations and aging of secondary org. aerosol (SOA) particles can alter their phys. and chem. properties, including particle morphol. Ammonia, one of the common atm. reactive constituents, can react with SOA particles, changing their properties and behavior. At low relative humidity, NH3 uptake by α-pinene SOA particles appears to be limited to the particle surface, which suggests that the reacted particles might not be homogeneous and have complex morphol. Here, we present a study aimed at detailed characterization of the effect of ammonia on the compn., d., morphol., shape, and evapn. kinetics of α-pinene SOA particles. We find that a small amt. of NH3 diffuses and reacts throughout the particle bulk, while most of the ammoniated products result from the reaction of NH3 with carboxylic acids on the particle surface, leading to a slight increase in particle size. We show that the reaction products form a solid semi-volatile coating that is a few nanometers thick. This solid coating prevents coagulating particles from coalescing for over two days. However, when the gas phase is dild. this semi-volatile coating evaps. in minutes, which is ensued by rapid coalescence. The ammoniated products in the particle bulk affect particles' evapn. kinetics, more so for the smaller particles that contain a higher fraction of ammoniated products.
      (b) Wilson, J.; Imre, D.; Beránek, J.; Shrivastava, M.; Zelenyuk, A. Evaporation Kinetics of Laboratory-Generated Secondary Organic Aerosols at Elevated Relative Humidity. Environ. Sci. Technol. 2015, 49, 243– 249,  DOI: 10.1021/es505331d
      21b
      Evaporation Kinetics of Laboratory-Generated Secondary Organic Aerosols at Elevated Relative Humidity
      Wilson, Jacqueline; Imre, Dan; Beranek, Josef; Shrivastava, Manish; Zelenyuk, Alla
      Environmental Science & Technology (2015), 49 (1), 243-249CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      Secondary org. aerosols (SOA) dominate atm. org. aerosols which affect climate, air quality, and health. Recent studies indicated that contrary to previously held assumptions, at low relative humidity (RH) these particles are semi-solid and evap. orders of magnitude slower than expected. Elevated relative humidity has the potential to significantly affect formation, properties, and atm. evolution of SOA particles. This work assessed the effect of RH on room temp. evapn. kinetics of SOA particles formed by ozonolysis of α-pinene and limonene. Expts. were conducted on α-pinene SOA particles generated, evapd., and aged at <5, 50, and 90% RH, and on limonene SOA particles at <5 and 90% RH. In all cases, evapn. began with a relatively fast phase, during which 30-70% of the particle mass evapd. in 2 h, followed by a much slower evapn. rate. Evapn. kinetics at <5 and 50% RH were nearly the same; at 90% RH, a slightly larger fraction evapd. In all cases, particle aging prior to induced evapn. reduced evaporative losses; aging at elevated RH led to a more significant effect. In all cases, obsd. SOA evapn. was nearly size-independent.
    22. 22
      Vaden, T. D.; Imre, D.; Beranek, J.; Shrivastava, M.; Zelenyuk, A. Evaporation kinetics and phase of laboratory and ambient secondary organic aerosol. Proc. Natl. Acad. Sci. U.S.A. 2011, 108, 2190– 2195,  DOI: 10.1073/pnas.1013391108
      22
      Evaporation kinetics and phase of laboratory and ambient secondary organic aerosol
      Vaden, Timothy D.; Imre, Dan; Beranek, Josef; Shrivastava, Manish; Zelenyuk, Alla
      Proceedings of the National Academy of Sciences of the United States of America (2011), 108 (6), 2190-2195, S2190/1-S2190/5CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)
      Field measurements of secondary org. aerosols (SOA) demonstrate significantly higher mass loads than those predicted by models, creating an intense effort focused on detg. addnl. SOA sources but leaving fundamental model assumptions unchallenged. Existing air quality models use absorptive partitioning theory and assume SOA particles are liq. droplets, forming an instantaneous reversible equil. with the gas phase. They ignore the effect of spectator org. species adsorption during SOA formation on SOA properties and fate. Using an accurate, highly sensitive exptl. approach to examine evapn. kinetics of size-selected, single SOA particles, the authors characterized room temp. evapn. kinetics of lab.-generated α-pinene and ambient atm. SOA. Even when gas phase orgs. were removed, it takes ∼24 h for pure α-pinene SOA particles to evap. 75% of their mass; this is in sharp contrast to the ∼10 min time scale predicted by existing kinetic models. Spectator org. vapor adsorption during SOA formation and the aging of these coated SOA particles dramatically reduced the evapn. rate; in some cases it nearly stopped it. Ambient SOA exhibited evapn. behavior very similar to that of lab.-generated, coated and aged SOA. For all cases assessed in this work, SOA evapn. behavior was nearly size-independent and did not follow evapn. kinetics of liq. droplets, in sharp contrast with model assumptions. Results concerning SOA phase, evapn. rate, and the importance of spectator gases and aging all indicated there is a need to reformulate the way SOA formation and evapn. are treated in models.
    23. 23
      Platt, S. M.; El Haddad, I.; Zardini, A. A.; Clairotte, M.; Astorga, C.; Wolf, R.; Slowik, J. G.; Temime-Roussel, B.; Marchand, N.; Ježek, I. Secondary organic aerosol formation from gasoline vehicle emissions in a new mobile environmental reaction chamber. Atmos. Chem. Phys. 2013, 13, 9141– 9158,  DOI: 10.5194/acp-13-9141-2013
      23
      Secondary organic aerosol formation from gasoline vehicle emissions in a new mobile environmental reaction chamber
      Platt, S. M.; El Haddad, I.; Zardini, A. A.; Clairotte, M.; Astorga, C.; Wolf, R.; Slowik, J. G.; Temime-Roussel, B.; Marchand, N.; Jezek, I.; Drinovec, L.; Mocnik, G.; Moehler, O.; Richter, R.; Barmet, P.; Bianchi, F.; Baltensperger, U.; Prevot, A. S. H.
      Atmospheric Chemistry and Physics (2013), 13 (18), 9141-9158, 18 pp.CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)
      We present a new mobile environmental reaction chamber for the simulation of the atm. aging of different emission sources without limitation from the instruments or facilities available at any single site. Photochem. is simulated using a set of 40 UV lights (total power 4 KW). Characterization of the emission spectrum of these lights shows that atm. aging of emissions may be simulated over a range of temps. (-7 to 25 °C). A photolysis rate of NO2, JNO2, of (8.0 ± 0.7) × 10-3 s-1 was detd. at 25°C. We demonstrate the utility of this new system by presenting results on the aging (OH = 12 × 106 cm-3 h) of emissions from a modern (Euro 5) gasoline car operated during a driving cycle (New European Driving Cycle, NEDC) on a chassis dynamometer in a vehicle test cell. Emissions from the entire NEDC were sampled and aged in the chamber. Total org. aerosol (OA; primary org. aerosol (POA) emission + secondary org. aerosol (SOA) formation) was (369.8-397.5) 10-3 g kg-1 fuel, or (13.2-15.4) × 10-3 g km-1, after aging, with aged OA/POA in the range 9-15. A thorough investigation of the compn. of the gas phase emissions suggests that the obsd. SOA is from previously unconsidered precursors and processes. This large enhancement in particulate matter mass from gasoline vehicle aerosol emissions due to SOA formation, if it occurs across a wider range of gasoline vehicles, would have significant implications for our understanding of the contribution of on-road gasoline vehicles to ambient aerosols.
    24. 24
      (a) Armentrout, P. B. Cation–ether complexes in the gas phase: thermodynamic insight into molecular recognition. Int. J. Mass Spectrom. 1999, 193, 227– 240,  DOI: 10.1016/S1387-3806(99)00165-7
      24a
      Cation-ether complexes in the gas phase: thermodynamic insight into molecular recognition
      Armentrout, P. B.
      International Journal of Mass Spectrometry (1999), 193 (2/3), 227-240CODEN: IMSPF8; ISSN:1387-3806. (Elsevier Science B.V.)
      Trends in the bond dissocn. energies for the binding of the alkali metal cations, Li+, Na+, K+, Rb+, and Cs+, to a series of ethers, 1-4 di-Me ethers, 1 and 2 dimethoxy ethanes, and the crown ethers, 12c4, 15c5, and 18c6, are discussed. The bond energies have been detd. in previous studies by anal. of the thresholds for collision-induced dissocn. of the cation-ether complexes by xenon as measured in a guided ion beam tandem mass spectrometer. Details of the anal. of the data are reviewed and the accuracy of the results ascertained by comparison with theor. results taken from the literature. Combined, the exptl. and theor. results provide an extensive thermochem. database for evaluation of the metal-crown complexes, a simple example of mol. recognition. These results indicate the importance of optimizing the metal-oxygen bond distances and the orientation of the local dipole on the oxygen towards the metal. Further, it is shown that excited state conformers of these complexes are probably obsd. in several systems as a result of interesting metal-dependent dynamics in the formation of the complexes.
      (b) More, M. B.; Ray, D.; Armentrout, P. B. Cation–Ether Complexes in the Gas Phase:  Bond Dissociation Energies of Na+(dimethyl ether)x, x = 1–4; Na+(1,2-dimethoxyethane)x, x = 1 and 2; and Na+(12-crown-4). J. Phys. Chem. A 1997, 101, 831– 839,  DOI: 10.1021/jp962851s
      24b
      Cation-Ether Complexes in the Gas Phase: Bond Dissociation Energies of Na+(dimethyl ether)x, x = 1-4; Na+(1,2-dimethoxyethane)x, x = 1 and 2; and Na+(12-crown-4)
      More, Michelle B.; Ray, Douglas; Armentrout, P. B.
      Journal of Physical Chemistry A (1997), 101 (5), 831-839CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
      Bond dissocn. energies of Na+[O(CH3)2]x, x = 1-4; Na+[(CH2OCH3)2]x, x = 1 and 2; and Na+[c-(C2H4O)4] are reported. The bond dissocn. energies are detd. exptl. by anal. of the thresholds for collision-induced dissocn. of the cation-ether complexes by xenon measured using guided ion beam mass spectrometry. In all cases, the primary and lowest energy dissocn. channel obsd. exptl. is endothermic loss of one ligand mol. The cross section thresholds are interpreted to yield 0 and 298 K bond dissocn. energies after accounting for the effects of multiple ion-mol. collisions, internal energy of the complexes, and unimol. decay rates. Trends in the bond dissocn. energies detd. by expt. and recent theor. ab initio calcns. are in good agreement. Our best exptl. values, which have an av. uncertainty of ±7 kJ/mol, are lower than the theor. values by 7 ± 5 kJ/mol per metal-oxygen interaction. These values are compared with bond dissocn. energies for the comparable lithium cation-ether complexes. This comparison reveals the thermodn. consequences of ligand-ligand repulsion.
    25. 25
      Lee, C. P.; Surdu, M.; Bell, D. M.; Dommen, J.; Xiao, M.; Zhou, X.; Baccarini, A.; Giannoukos, S.; Wehrle, G.; Schneider, P. A. High-frequency gaseous and particulate chemical characterization using extractive electrospray ionization mass spectrometry (Dual-Phase-EESI-TOF). Atmos. Meas. Tech. 2022, 15, 3747– 3760,  DOI: 10.5194/amt-15-3747-2022
      25
      High-frequency gaseous and particulate chemical characterization using extractive electrospray ionization mass spectrometry (Dual-Phase-EESI-TOF)
      Lee, Chuan Ping; Surdu, Mihnea; Bell, David M.; Dommen, Josef; Xiao, Mao; Zhou, Xueqin; Baccarini, Andrea; Giannoukos, Stamatios; Wehrle, Gunther; Schneider, Pascal Andre; Prevot, Andre S. H.; Slowik, Jay G.; Lamkaddam, Houssni; Wang, Dongyu; Baltensperger, Urs; El Haddad, Imad
      Atmospheric Measurement Techniques (2022), 15 (12), 3747-3760CODEN: AMTTC2; ISSN:1867-8548. (Copernicus Publications)
      To elucidate the sources and chem. reaction pathways of org. vapors and particulate matter in the ambient atm., real-time detection of both the gas and particle phase is needed. State-of-the-art techniques often suffer from thermal decompn., ionization-induced fragmentation, high cut-off size of aerosols or low time resoln. In response to all these limitations, we developed a new technique that uses extractive electrospray ionization (EESI) for online gas and particle chem. speciation, namely the dual-phase extractive electrospray ionization time-of-flight mass spectrometer (Dual-Phase-EESI-TOF or Dual-EESI for short). The Dual-EESI was designed and optimized to measure gas- and particle-phase species with satn. vapor concns. spanning more than 10 orders of magnitude with good linearity and a measurement cycle as fast as 3 min. The gas-phase selectivity of the Dual-EESI was compared with that of nitrate chem. ionization mass spectrometry. In addn., we performed org. aerosol uptake expts. to characterize the relative gas and particle response factors. In general, the Dual-EESI is more sensitive toward gas-phase analytes as compared to their particle-phase counterparts. The real-time measurement capability of the Dual-EESI for chem. speciated gas- and particle-phase measurements can provide new insights into aerosol sources or formation mechanisms, where gas-particle partitioning behavior can be detd. after abs. parameterization of the gas / particle sensitivity.
    26. 26
      Clark, C. H.; Nakao, S.; Asa-Awuku, A.; Sato, K.; Cocker, D. R. Real-Time Study of Particle-Phase Products from α-Pinene Ozonolysis and Isoprene Photooxidation Using Particle into Liquid Sampling Directly Coupled to a Time-of-Flight Mass Spectrometer (PILS-ToF). Aerosol Sci. Technol. 2013, 47, 1374– 1382,  DOI: 10.1080/02786826.2013.844333
      26
      Real-Time Study of Particle-Phase Products from α-Pinene Ozonolysis and Isoprene Photooxidation Using Particle into Liquid Sampling Directly Coupled to a Time-of-Flight Mass Spectrometer (PILS-ToF)
      Clark, Christopher H.; Nakao, Shunsuke; Asa-Awuku, Akua; Sato, Kei; Cocker, David R.
      Aerosol Science and Technology (2013), 47 (12), 1374-1382CODEN: ASTYDQ; ISSN:0278-6826. (Taylor & Francis, Inc.)
      A particle into liq. sampler (PILS) has been directly coupled to an accurate mass atm. ionization time-of-flight mass spectrometer (TOF) for use in the speciation of secondary org. aerosol (SOA) formed in the University of California-Riverside, College of Engineering-Center for Environmental Research and Technol. (CE-CERT) atm. chambers. To this end, the PILS has been optimized for direct continuous injection into the ToF and the PILS-ToF system has been used to obtain real-time mass spectral traces of the particle phase products of atm. chamber reactions. The PILS-ToF system has been initially applied to SOA formed from α-pinene dark ozonolysis and isoprene photooxidn. The characterization of the PILS-TOF system includes expts. on the well understood α-pinene/O3 system, which verifies the performance of the tool. The PILS-TOF tool is then used to provide new insight into the chem. compn. of the SOA formed from isoprene photooxidn. For the first time, time resolved traces of oligomer formation during isoprene photooxidn. are obsd. using the PILS-TOF. The unique subunits of oligomer series are reported. The PILS-TOF system is demonstrated to be a powerful tool for obtaining real-time electro spray ionization and chem. ionization mass spectral speciation of aerosols.Copyright 2013 American Assocn. for Aerosol Research.
    27. 27
      (a) Romonosky, D. E.; Li, Y.; Shiraiwa, M.; Laskin, A.; Laskin, J.; Nizkorodov, S. A. Aqueous Photochemistry of Secondary Organic Aerosol of α-Pinene and α-Humulene Oxidized with Ozone, Hydroxyl Radical, and Nitrate Radical. J. Phys. Chem. A 2017, 121, 1298– 1309,  DOI: 10.1021/acs.jpca.6b10900
      27a
      Aqueous Photochemistry of Secondary Organic Aerosol of α-Pinene and α-Humulene Oxidized with Ozone, Hydroxyl Radical, and Nitrate Radical
      Romonosky, Dian E.; Li, Ying; Shiraiwa, Manabu; Laskin, Alexander; Laskin, Julia; Nizkorodov, Sergey A.
      Journal of Physical Chemistry A (2017), 121 (6), 1298-1309CODEN: JPCAFH; ISSN:1089-5639. (American Chemical Society)
      Formation of secondary org. aerosols (SOA) from biogenic volatile org. compds. (BVOC) occurs via O3- and OH-initiated reactions during the day and reactions with NO3 during the night. We explored the effect of these three oxidn. conditions on the mol. compn. and aq. photochem. of model SOA prepd. from two common BVOC. A common monoterpene, α-pinene, and sesquiterpene, α-humulene, were used to form SOA in a smog chamber via BVOC + O3, BVOC + NO3, and BVOC + OH + NOx oxidn. Samples of SOA were collected on filters, water-sol. compds. from SOA were extd. in water, and the resulting aq. solns. were photolyzed to simulate the photochem. aq. processing of SOA. The extent of change in the mol. level compn. of SOA over 4 h of photolysis (approx. equiv. to 64 h of photolysis under ambient conditions) was assessed with high-resoln. electrospray ionization mass spectrometry. The anal. revealed significant differences in the mol. compn. between SOA formed by the different oxidn. pathways. The compn. further evolved during photolysis with the most notable change corresponding to the nearly complete removal of nitrogen-contg. org. compds. Hydrolysis of SOA compds. also occurred in parallel with photolysis. The preferential loss of larger SOA compds. during photolysis and hydrolysis made the SOA compds. more volatile on av. This study suggests that aq. processes may under certain conditions lead to a redn. in the SOA loading as opposed to an increase in SOA loading commonly assumed in the literature.
      (b) Pospisilova, V.; Lopez-Hilfiker, F. D.; Bell, D. M.; El Haddad, I.; Mohr, C.; Huang, W.; Heikkinen, L.; Xiao, M.; Dommen, J.; Prevot, A. S. H. On the fate of oxygenated organic molecules in atmospheric aerosol particles. Sci. Adv. 2020, 6, eaax8922  DOI: 10.1126/sciadv.aax8922
      There is no corresponding record for this reference.

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    • Description of iterative solution for sensitivity, experimental design, schematic of the EESI inlet, average size distributions measured by the SMPS for PEG-300, fraction evaporating from PEG-300 for each specific species, comparison of the EESI mass concentrations with sensitivity conversion (in Figure 2A) from ag s-1 to μg m-3 to the measured SMPS mass concentration, fraction remaining of the monomer and dimer regions aggregated by oxygen number as a function of TD temperature, mass weighted size distributions, and mass concentration comparison (PDF)


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