Potentiometric sensors that exhibit a non-Hofmeister selectivity sequence are normally designed by selective chemical recognition elements in the membrane. In other situations, when used as detectors in separation science, for example, membranes that respond equally to most ions are preferred. With so-called liquid membranes, a low selectivity is difficult to accomplish since these membranes are intrinsically responsive to lipophilic species. Instead, the high solubility of sample lipids in an ionophore-free sensing matrix results in a deterioration of the response. We explore here potentiometric sensors on the basis of ion-exchange membranes commonly used in fuel cell applications and electrodialysis, which have so far not found their way into the field of ion-selective electrodes. These membranes act as Donnan exclusion membranes as the ions are not stripped of their hydration shell as they interact with the membrane. Because of this, lipophilic ions are no longer preferred over hydrophilic ones, making them promising candidates for the detection of abundant ions in the presence of lipophilic ones or as detectors in separation science. Two types of cation-exchanger membranes and one anion-exchange membrane were characterized, and potentiometric measuring ranges were found to be Nernstian over a wide range down to about 10 μM concentrations. Depending on the specific membrane, lipophilic ions gave equal response to hydrophilic ones or were even somewhat discriminated. The medium and long-term stability and reproducibility of the electrode signals were found to be promising when evaluated in synthetic and whole blood samples.
Researchers have been aiming to improve ion-selective electrode selectivity for numerous decades. The simplest liquid or polymeric membranes are composed of lipophilic ion-exchanging salts dissolved in a water-immiscible organic solvent. Their selectivity is based on the energy of transfer of ions from the aqueous sample to the membrane phase and therefore on ion lipophilicity. This order of preference is well established as the Hofmeister selectivity sequence.
When used as detectors in separation science, potentiometric sensors should ideally respond to all eluted ions equally. This is difficult to accomplish with the principle outlined above since more lipophilic ions will typically give a larger signal, with the exception of dilute interferences (Hulanicki effect) and short readout time (kinetic discrimination). When these effects apply, the potentiometric sensors respond equally to all ions in the sample. (1) On the other hand, the detection of abundant ions in physiological samples may also be hampered by the presence of dilute but lipophilic species, for example, thiocyanate or salicylate for the detection of chloride in blood. (2) Moreover, the hydrophobic nature of the membrane has been found to result in a substantial extraction of lipids from the sample, drastically altering the membrane matrix and resulting in unacceptable sensor drifts. (3) These undesired effects can be mitigated to some extent by the use of ionophores (ion carriers) in the membrane phase. Many such ionophores have been introduced in the past few decades, and their aim is to achieve a selectivity pattern that deviates from the Hofmeister selectivity sequence. (4) While this has been an important success story in the field, numerous applications exist where a better tolerance to lipid compounds, organic solvents, and higher temperature are desired.
This has recently initiated the search for alternate membrane materials that are not lipid-like, chiefly by the use of fluorous membrane materials as put forward by the group of Buhlmann. (5, 6) Such membrane materials reject hydrophilic and hydrophobic species and represent an important new direction in ion sensor development.
More recently, Gyurcsanyi reported on a new class of potentiometric sensors based on chemically functionalized nanopore membranes. (7) These pores are understood as high charge density nanochannels where the passage of charge is dictated by Donnan exclusion effects. Such materials are very promising because they are solvent free and can potentially make use of water-soluble biochemical receptors as well.
Similarly structured nanochannels are thought to also be present in ion exchange Donnan exclusion membranes (IEDEM), whose exact structure and mechanism is still being debated (for more details, see refs 8−10). Nonetheless, a vast amount of applications in fuel cells, electrochemistry, and electrodialysis has been reported employing this class of membranes. (-11-17)
Nafion is perhaps the most prominent example of IEDEM that is composed by a tetrafluoroethylene-based polymer substituted with sulfonate groups. (18-21) Recent work by Schmidt-Rohr’s group suggests that the charge transport occurs along nanopores of high charge density, thereby forming hydrated channels with diameters on the order of 2.5 nm. (22, 23) The high sulfonate density gives the polymer its ion-exchanging properties by Donnan exclusion while the structure of the backbone gives excellent mechanical, chemical, and thermal stability while not serving as a solvent. Because of the lack of a traditional solvent extraction process, this polymer does not exhibit a selectivity pattern based on the lipophilicity of ions as with the ion-exchanger-based solvent polymeric membranes discussed above.
Early work reporting on the potentiometric response characteristics of unmodified or “bare” Nafion membranes exhibited a very limited measuring range, (24) and this result has perhaps discouraged progress in this area. Despite the documented benefits of such materials, only a limited number of reports on using IEDEM as potentiometric sensor materials have appeared in the literature. (25, 26) In contrast, we find here that commercially available ion-exchange membranes are well suited for this purpose, with a wide response range and an attractive selectivity for selected applications.
Experimental Section
Click to copy section linkSection link copied!
Reagents, Materials, and Equipment
Aqueous solutions were prepared by dissolving the appropriate salts in deionized water (>18 MΩ cm). FKL (cation-exchanging) and FAB (anion-exchanging) membranes, both of thicknesses of 100 μm, were purchased from Fumatech (FuMA-Tech GmbH, Am Grubenstollen 11, 66386 St. Ingbert, Germany) while Nafion membrane NR-211 of a thickness of 25 μm was obtained from Ion Power (Inc. 720 Governor Lea Rd, New Castle, DE 19720). Membranes of 7 mm diameter were punched from the parent membrane and mounted in OSTEC bodies (Oesch Sensor Technology AG, Ragazerstrasse 35, 320 Sargans, Switzerland). A solution of 10 mM NaCl was used as the inner electrolyte. FAB membranes were stored in 4 g L–1 NaCl + 0.1 g L–1 NaN3 solution before electrode preparation, while cation-selective membranes were used as obtained. Potentiometric measurements were taken against a double-junction Ag/AgCl/sat. KCl/1 M LiOAc reference electrode (Metrohm AG, Ionenstrasse, CH-9100 Herisau, Switzerland), using a 16-channel EMF interface (Lawson Laboratories, Inc., Malvern, PA). All experiments were carried out at laboratory ambient temperature of 22 °C.
Procedures
Selectivity measurements were performed by adding appropriate aliquots of salts and evaluated using the modified separate solutions method. (27) The obtained separate calibration curves were extrapolated to 1 M, and the selectivity coefficient was calculated from this potential difference by dividing by the theoretical slope of 59.2 mV. (28) The activities of the ions were calculated with a two-parameter Debye–Hückel approximation. (29)
Sodium and chloride ions analysis in undiluted whole blood was performed at 22 °C. Before analysis, the sample was heated up in a water bath to ambient temperature. For the standard addition procedure, electrodes were left in continuous contact with undiluted heparinized human blood (5 U/mL heparin, University Hospital of Geneva, HUG) for 1 h to evaluate possible potential drifts in this sample matrix. NaCl additions increased its concentration in blood by 0.029, 0.057, 0.90, 0.152, and 0.231 M, while for KSCN the concentration was being changed by concentration steps of 1 order of magnitude in the 10–6–10–2 M range. External calibration before and after contact with blood (5 min contact time) was performed with 0.03, 0.1, and 0.3 M NaCl solutions. The entire procedure was repeated twice for each electrode.
Results and Discussion
Click to copy section linkSection link copied!
Unlike classical organic solvent-based membranes used for decades in potentiometry, ion-exchange membranes used for electrodialysis applications exhibit highly reduced selectivity toward different ions. Polar groups (sulfonic or quaternary ammonium) present in high concentration within the polymer structure form aggregates allowing a water content of up to 50 vol % in the membrane phase. Ion-exchange may only take place at the water–polymer interface without ion extraction into the polymer phase. As a result, the selectivity is expected to be less dependent on ion lipophilicity (see below Table 1) and more on Coulombic interactions. Moreover, possible diffusion potential contributions may arise in the case of mixed ion solutions. (30)
Table 1. Potentiometric Selectivity Characteristics of Ion-Exchange Membranes
membrane
ion (J)
slope (mV)
EJ° (mV)
log(KI,Jpot)
FAB
Cl–
–57.8 ± 0.3
13.5 ± 0.7
0
ClO4–
–60.5 ± 0.6
–78.9 ± 3.4
1.5 ± 0.1
SCN–
–58.4 ± 0.9
–75.4 ± 4.2
1.5 ± 0.1
NO3–
–57.7 ± 1.0
–19.4 ± 3.1
0.5 ± 0.1
Nafion
Na+
59.5 ± 0.3
242.2 ± 2.7
0
Li+
61.5 ± 0.1
243.5 ± 0.3
0.02 ± 0.01
K+
56.7 ± 0.2
245.8 ± 1.2
0.06 ± 0.02
Ca2+
57.8 ± 0.6
250.7 ± 2.5
0.15 ± 0.08
Mg2+
60.3 ± 0.9
256.8 ± 2.5
0.5 ± 0.1
FKL
Na+
51.5 ± 0.4
255.1 ± 2.5
0
Li+
51.9 ± 0.8
230.2 ± 3.6
–0.4 ± 0.1
K+
64.8 ± 0.6
289.3 ± 0.7
0.6 ± 0.1
Ca2+
59.4 ± 2.5
287.1 ± 6.1
1.1 ± 0.3
Mg2+
58.4 ± 3.4
284.1 ± 5.1
1.0 ± 0.3
Nafion, FKL, and FAB electrodialysis membranes were studied here in potentiometry. Three electrodes of each type were prepared, and their working characteristics were evaluated with Na+, K+, Li+, Ca2+, and Mg2+ for cation-exchange membranes and Cl–, ClO4–, SCN–, NO3–, and OAc– for anion-exchanging ones. Figure 1 shows the corresponding calibration curves upon adding aliquots of NaCl to the sample solution with pure water as background. The key characteristics are summarized in Table 1. The estimated error in Table 1 is a result of three calibrations performed during the same day (n = 3). Calibrations were also repeated three times on consecutive days but only for the primary analyte (giving a RSD ≤ 0.5%) All membranes responded rapidly (t95 ≤ 5 s) to concentration changes in the contacting solution, giving a stable signal. Short-term stabilities (3 min) were extracted from Figure 1. The drift (EMF/time) after each addition gives us information about the stability at short times, giving 0.1 mV min–1 for cation exchange and membranes and 0.02 mV min–1 for anion exchange membranes on average. Long-term stability was evaluated over 15 h in the presence of 0.1 mM CaCl2 and 100 mM NaCl using a concentrated NaCl solution as inner solution (see Figure 1S, Supporting Information). For FAB (0.05 mV h–1) and FKL (0.4 mV h–1), the obtained values are promising for practical applications. Nafion membranes showed a considerably higher drift (2 mV h–1). All electrodes responded with a theoretical slope within a 10 μM to 300 mM NaCl concentration range.
Figure 1
Figure 1. Potentiometric calibration curves and associated time responses to NaCl additions with the following membranes: (A) FKL (anion-exchange), (B) Nafion, and (C) FAB (both cation-exchange); see Experimental Section.
In contrast to established liquid membrane cation-selective electrodes, cation-exchange membranes responded to divalent cations with a monovalent slope; see Figure 2S in the Supporting Information. For Nafion membranes, this behavior was observed until the divalent ion concentration in the solution approached that of NaCl in the inner electrolyte, after which point only the expected divalent ion slope was observed. On the other hand, when the membranes were conditioned in divalent cations such as Ca2+ for one day, a Nernstian response slope of 29.8 mV was found for both divalent and monovalent ions (Na+) (see Figure 3S in the Supporting Information). This peculiar effect cannot be readily explained, but it is clearly related to kinetic, rather than thermodynamic, characteristics of the membrane.
The strength of the Coulombic interaction should increase with increasing ion charge, but the data presented in Table 1 suggest that any such interaction translates in a rather weak potentiometric preference.
With anion exchange membranes, ion-exchange theory predicts that ions with smaller hydrodynamic (stokes) radii should interact more weakly with the ion-exchanger. Indeed, perchlorate and thiocyanate, by virtue of their weaker hydration, are preferred over better hydrated ions such as chloride (see Table 1). As with the cation-selective membranes, and also in some analogy to liquid membrane ion-selective electrodes, the calibration curves were found to be most linear if the membrane was conditioned with the ion to be measured (in this case both Na+ and Cl–) . While hydrodynamic radii do impose a selectivity pattern on the membrane response, the magnitude of this effect is dramatically smaller than with established anion-selective electrodes. With polymeric liquid membranes, for example, perchlorate is typically preferred by about 4.5 orders of magnitude over chloride, (31) giving rise to a ca. −270 mV potential change at the same concentration (compared to the −89 mV shown in Table 1).
This type of behavior is very much desired if the electrode is applied as a detector together with a separation technique. One additional potential advantage of nonselective membranes is, however, when the analyte of interest is in excess to a dilute but much more lipophilic interfering ion. This situation is for example observed with sodium and chloride ions in the presence of potassium, thiocyanate, or salicylate in blood samples. The sodium concentration in blood plasma is about 140 mM, while potassium levels are about 30 times lower. For chloride and thiocyanate ions, the difference is even larger, with 95–110 mM chloride compared to at least a thousand times less thiocyanate. Modern ionophore-based potentiometric sensors for sodium exhibit the required selectivity for analysis of sodium in blood. For the detection of chloride, on the other hand, thiocyanate and salicylate may be a serious interference owing to its greater lipophilicity.
Electrodes with each of the three studied ion-exchanging membranes were explored in the analysis of sodium and chloride in blood samples. Figure 2 presents results of NaCl additions to blood for electrodes with FKL and FAB membranes. Electrode potentials changed by at most 2.7 and −2.8 mV for FKL and FAB membranes, respectively, during continuous contact with undiluted heparinized human blood for half an hour. All of them also responded quickly (t95 ≤ 5 s) to a 0.03 M NaCl addition, which corresponds to a ca. 20% concentration increase for sodium and about 30% for chloride. The standard addition calibration gave a linear response for both ions, suggesting an absence of interferences from other ions present in the sample. In the case of Nafion membranes, trans-membrane fluxes resulted in significant potential drifts and made the analysis unreliable (see Figure 4S in the Supporting Information). To confirm the lack of interferences from potassium and thiocyanate, standard additions of KSCN were performed in blood. A significant electrode response was only found at a concentration of 10–2 M KSCN, which is significantly outside the physiologically possible concentration range and therefore of no concern in practice. Moreover, therapeutic concentrations of salicylate (720 μM) were confirmed not to interfere with the chloride response at 0.1 M NaCl, see Figure 5S in the Supporting Information, giving a mere 75 μV potential response.
Figure 2
Figure 2. Potentiometric response of FKL (top) and FAB (bottom) membranes upon exposure to whole blood samples and subsequent standard additions of NaCl.
While a careful clinical evaluation is outside the scope of this work, preliminary data on blood assays using repeated external calibrations are presented here to encourage further work in this direction. Figure 3 demonstrates external calibrations for the FAB and FKL membranes in electrolyte solutions followed by exposure to blood for 30 min. The data suggest attractive analytical stability, especially for the anion-exchanging membrane where reproducibilities of the electrode potential in the external calibration readings were just 1.3 mV while the deviations in potential readings during contact with blood were below 0.8 mV.
Figure 3
Figure 3. Repeated external calibrations, each followed by a 30 min exposure to whole blood for the FKL (top) and FAB (bottom) membrane-based ion-selective electrodes.
Ion-exchange membranes such as FKL or FAB are a promising class of alternate materials in the design of potentiometric sensors. Their fast and stable response makes them attractive candidates for situations where their added ruggedness (compared to liquid or plasticized polymeric membranes) and their selectivity characteristics are of interest. In contrast to liquid ion-exchanger-based ion-selective membranes, FKL and FAB membranes show no preference to lipophilic ions, although the selectivity is a function of the hydrodynamic radius of the ion. They may be of particular interest to the analysis of abundant hydrophilic ions where lipids and lipophilic ions ordinarily give rise to serious interference. It was shown here that these membranes allow one to detect sodium and chloride ions in undiluted whole blood sample, even in the presence of an excess of potassium and thiocyanate/salicylate ions over physiologically possible levels. An application not yet explored here and for which the membranes are expected to be attractive as well as their use as detectors in separation science.
Supporting Information
Click to copy section linkSection link copied!
Additional information as noted in text. This material is available free of charge via the Internet at http://pubs.acs.org.
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
Click to copy section linkSection link copied!
Corresponding Author
Eric Bakker - Department of Inorganic and Analytical
Chemistry, University of Geneva, Quai E.-Ansermet
30, CH-1211
Geneva, Switzerland;
Email: [email protected]
Authors
Ewa Grygolowicz-Pawlak - Department of Inorganic and Analytical
Chemistry, University of Geneva, Quai E.-Ansermet
30, CH-1211
Geneva, Switzerland
Gastón A. Crespo - Department of Inorganic and Analytical
Chemistry, University of Geneva, Quai E.-Ansermet
30, CH-1211
Geneva, Switzerland
Majid Ghahraman Afshar - Department of Inorganic and Analytical
Chemistry, University of Geneva, Quai E.-Ansermet
30, CH-1211
Geneva, Switzerland
Günter Mistlberger - Department of Inorganic and Analytical
Chemistry, University of Geneva, Quai E.-Ansermet
30, CH-1211
Geneva, Switzerland
Notes
The authors declare no competing financial interest.
Acknowledgment
Click to copy section linkSection link copied!
The authors thank the Swiss National Science Foundation for supporting this research. This work also forms part of a project funded by the Australian Research Council (DP0987851).
Salicylate interference with the Roche Cobas Integra chloride electrode. Comments
Mori, Leonard; Waldhuber, Susan
Clinical Chemistry (Washington, D. C.)
(1997),
43
(7),
1249-1250CODEN:
CLCHAU;
ISSN:0009-9147.
(American Association for Clinical Chemistry)
Interference by salicylate on the title electrode leads to abnormally high chloride values which are not found when other brand electrodes are used. Patients showing unexplained high Cl- results on the Integra with a large neg. anion-cation gap should be investigated for salicylate ingestion.
A highly selective, sensitive, fast, and stable amperometric sensor for the detn. of hydrogen peroxide residues in aseptic milk is presented. To fabricate this amperometric sensor, a thin film of Prussian blue was first electrodeposited on a glassy carbon electrode and then a Nafion polymer layer was formed on the top. It was found that Nafion film greatly improves the anti-interference ability and the stability of the Prussian blue-modified electrode. Factors that influence the overall anal. performance of the sensor, such as the concn. of Nafion drop and pH value of the electrolyte, were examd. Results show that the prepd. sensor possesses efficient electrocatalytic activity towards hydrogen peroxide with the detection limit as low as 0.2 μM and linear range from 0.8 μM to 0.12 mM. The developed sensor was applied to the detn. of hydrogen peroxide in milk with satisfactory results.
Extremely stable Nafion based carbon monoxide sensor
van der Wal, P. D.; de Rooij, N. F.; Koudelka-Hep, M.
Sensors and Actuators, B: Chemical
(1996),
35
(1-3),
119-123CODEN:
SABCEB;
ISSN:0925-4005.
(Elsevier)
Carbon monoxide sensors using Nafion solid polymer electrolyte are described. Dry Nafion sensors showed stability problems; on the other hand sensors equipped with a water reservoir (wet Nafion sensors) were extremely stable. The proposed manufg. technol., compatible with hybrid technol. is suitable for cheap mass fabrication.
Chemical Reviews (Washington, DC, United States)
(2004),
104
(10),
4535-4585CODEN:
CHREAY;
ISSN:0009-2665.
(American Chemical Society)
A review on morphol. characterization using X-rays and neutrons, microscopy studies, mech. properties, mol. simulations, and the nature of aq. and nonaq. solvents and ions in Nafions.
The structure of the Nafion ionomer used in proton-exchange membranes of H2/O2 fuel cells has long been contentious. Using a recently introduced algorithm, we have quant. simulated previously published small-angle scattering data of hydrated Nafion. The characteristic 'ionomer peak' arises from long parallel but otherwise randomly packed water channels surrounded by partially hydrophilic side branches, forming inverted-micelle cylinders. At 20 vol% water, the water channels have diams. of between 1.8 and 3.5 nm, with an av. of 2.4 nm. Nafion crystallites (∼10 vol%), which form phys. crosslinks that are crucial for the mech. properties of Nafion films, are elongated and parallel to the water channels, with cross-sections of ∼(5 nm)2. Simulations for various other models of Nafion, including Gierke's cluster and the polymer-bundle model, do not match the scattering data. The new model can explain important features of Nafion, including fast diffusion of water and protons through Nafion and its persistence at low temps.
The water-polymer interfacial area per vol., S/V, which is reflected in the Porod region of small-angle scattering data, is an important parameter of different models of the Nafion fuel cell membrane. Therefore, published exptl. S/V data of Nafion are compared over a wide range of hydration levels with various structural models featuring stiff polymer backbones, in particular the parallel water-channel and the polymer ribbon models. The S/V curve at intermediate hydration levels typical of fuel-cell conditions (ca. 20 vol% water) matches that of the parallel water-channel model with mol. corrugation. At higher hydration levels, i.e. for membranes soaked in water or autoclaved at elevated pressures, the polymer-ribbon model matches the decreasing S/V ratio with increasing water content, while the polymer-bundle model predicts a higher surface area. However, the ribbon or bundle models cannot apply at low hydration (< 3 water mols. per Nafion side group), since it is shown that the interfacial area in this regime must increase strongly with hydration, being detd. by the available surface area of the water mols. The pronounced asymmetry of the plot of S/V vs. water vol. fraction is explained in terms of the difference in the diams. of the water mols. and the polymer aggregates.
A new procedure for the detn. of selectivity coeffs. of neutral carrier-based cation-selective electrodes is established that avoids exposure to the preferred ion prior to the measurement of discriminated ions. The method is, therefore, unbiased by the presence of preferred ions in the membrane that otherwise could mask the response to discriminated ion solns. It is generally applicable as long as considerations are met and can only be applied once for a given membrane. Careful studies with sodium-, silver-, and calcium-selective electrodes reveal that Nernstian response slopes can now be obtained for even highly discriminated cations. Specifically, a 1,3-bridged calix[4]arene deriv. as introduced by Yamamoto and Shinkai indeed yields an extraordinary sodium selectivity of log KNa,Kpot = -4.9, with potassium showing Nernst response as well. Analogous measurements with two different silver carriers, a bisthioether-functionalized calix[4]arene and methylenebis(diisobutyldithiocarbamate), and the calcium carrier ETH 129 also show extremely high selectivity, which can satisfactorily be correlated to data obtained previously in ion-buffered solns. The new procedure promises to be a valuable addnl. tool for future characterizations of highly selective ion carriers.
A review, with 29 refs., is given. Selectivities of solvent polymeric membrane ion-selective electrodes (ISEs) are quant. related to equil. at the interface between the sample and the electrode membrane. However, only correctly detd. selectivity coeffs. allow accurate predictions of ISE responses to real-world samples. also, they are also required for the optimization of ionophore structures and membrane compns. Best suited for such purposes are potentiometric selectivity coeffs. as defined already in the 1960s. This paper briefly reviews the basic relations and focuses on possible biases in the detn. of selectivity coeffs. The traditional methods to det. selectivity coeffs. (sep. soln. method, fixed interference method) are still the same as those originally proposed by IUPAC in 1976. However, several precautions are needed to obtain meaningful data. For example, errors arise when the response to a weakly interfering ion is also influenced by the primary ion leaching from the membrane. Wrong selectivity coeffs. may be also obtained when the interfering agent is highly preferred and the electrode shows counterion interference. Recent advances show how such pitfalls can be avoided. A detailed recipe to det. correct potentiometric selectivity coeffs. unaffected by such biases is presented.
Among the published formula for the calcn. of mean activity coeffs., the most reliable and comprehensive are those recently recommended by the National Burea of Stds. In many applications, the ionic strength does not exceed ∼1 M, and the NBS functions can be approximated by a 2-parameter Debye-Hueckel model. The limits of applicability (e.g., 1% deviation from the corresponding NBS model) are listed. The procedure makes efficient use of calculator memory.
The theory of coupled diffusion of multiple ionic species based on complete Donnan exclusion is applied to a diffusion process involving an ion-exchange membrane and three counter ions. The effect of the main process parameters (e.g., diffusion coeffs. and ionic charges) was studied by numerical simulations. The results obtained underline the importance of taking into account the coupled diffusion of all counter ions in a multi-ion system to describe adequately the transport of each individual counter ion.
There is no corresponding record for this reference.
Cited By
Click to copy section linkSection link copied!
This article is cited by 52 publications.
Atsushi Kishioka, Yufuku Matsushita, Masafumi Miyake. Detection of Interfering Ions Using Ion Flux Phenomena in Flow-Through Cl-ISEs with Ion Exchange Membranes. Analytical Chemistry2023, 95
(19)
, 7584-7593. https://doi.org/10.1021/acs.analchem.3c00366
Yujie Liu, Rocío Cánovas, Gastón A. Crespo, María Cuartero. Thin-Layer Potentiometry for Creatinine Detection in Undiluted Human Urine Using Ion-Exchange Membranes as Barriers for Charged Interferences. Analytical Chemistry2020, 92
(4)
, 3315-3323. https://doi.org/10.1021/acs.analchem.9b05231
Lifu Chen, Richard G. Compton. Reference Electrodes for Electrochemical Sensors Based on Redox Couples Immobilized within Nafion Films. ACS Sensors2019, 4
(6)
, 1716-1723. https://doi.org/10.1021/acssensors.9b00693
María Cuartero, Gastón A. Crespo. Using Potentiometric Electrodes Based on Nonselective Polymeric Membranes as Potential Universal Detectors for Ion Chromatography: Investigating an Original Research Problem from an Inquiry-Based-Learning Perspective. Journal of Chemical Education2018, 95
(12)
, 2172-2181. https://doi.org/10.1021/acs.jchemed.8b00455
Rebecca
H. Palmer, Chung-Wei Kung, Jian Liu, Omar K. Farha, Joseph T. Hupp. Nickel–Carbon–Zirconium Material Derived from Nickel-Oxide Clusters Installed in a Metal–Organic Framework Scaffold by Atomic Layer Deposition. Langmuir2018, 34
(47)
, 14143-14150. https://doi.org/10.1021/acs.langmuir.8b02166
Suphasinee Sateanchok, Nadezda Pankratova, Maria Cuartero, Thomas Cherubini, Kate Grudpan, Eric Bakker. In-Line Seawater Phosphate Detection with Ion-Exchange Membrane Reagent Delivery. ACS Sensors2018, 3
(11)
, 2455-2462. https://doi.org/10.1021/acssensors.8b01096
Jinbo Hu, Wenyang Zhao, Philippe Bühlmann, Andreas Stein. Paper-Based All-Solid-State Ion-Sensing Platform with a Solid Contact Comprising Colloid-Imprinted Mesoporous Carbon and a Redox Buffer. ACS Applied Nano Materials2018, 1
(1)
, 293-301. https://doi.org/10.1021/acsanm.7b00151
Nadezda Pankratova, Maria Cuartero, Thomas Cherubini, Gaston A. Crespo, and Eric Bakker . In-Line Acidification for Potentiometric Sensing of Nitrite in Natural Waters. Analytical Chemistry2017, 89
(1)
, 571-575. https://doi.org/10.1021/acs.analchem.6b03946
Majid Ghahraman Afshar, Gastón A. Crespo, and Eric Bakker . Flow Chronopotentiometry with Ion-Selective Membranes for Cation, Anion, and Polyion Detection. Analytical Chemistry2016, 88
(7)
, 3945-3952. https://doi.org/10.1021/acs.analchem.6b00141
Shogo Ogawara, Jesse L. Carey, III, Xu U. Zou, and Philippe Bühlmann . Donnan Failure of Ion-Selective Electrodes with Hydrophilic High-Capacity Ion-Exchanger Membranes. ACS Sensors2016, 1
(1)
, 95-101. https://doi.org/10.1021/acssensors.5b00128
Jesse L. Carey, III, David R. Whitcomb, Suyue Chen, R. Lee Penn, and Philippe Bühlmann . Potentiometric in Situ Monitoring of Anions in the Synthesis of Copper and Silver Nanoparticles Using the Polyol Process. ACS Nano2015, 9
(12)
, 12104-12114. https://doi.org/10.1021/acsnano.5b05170
Maria Cuartero, Gastón A. Crespo, and Eric Bakker . Paper-Based Thin-Layer Coulometric Sensor for Halide Determination. Analytical Chemistry2015, 87
(3)
, 1981-1990. https://doi.org/10.1021/ac504400w
Maria Cuartero, Gastón A. Crespo, Majid Ghahraman Afshar, and Eric Bakker . Exhaustive Thin-Layer Cyclic Voltammetry for Absolute Multianalyte Halide Detection. Analytical Chemistry2014, 86
(22)
, 11387-11395. https://doi.org/10.1021/ac503344f
Jing Zhang, Yun Zhao, Chun-Ge Yuan, Li-Na Ji, Xiao-Dong Yu, Feng-Bin Wang, Kang Wang, and Xing-Hua Xia . Donnan Potential Caused by Polyelectrolyte Monolayers. Langmuir2014, 30
(33)
, 10127-10132. https://doi.org/10.1021/la502320m
Majid Ghahraman Afshar, Gastón A. Crespo, Xiaojiang Xie, and Eric Bakker . Direct Alkalinity Detection with Ion-Selective Chronopotentiometry. Analytical Chemistry2014, 86
(13)
, 6461-6470. https://doi.org/10.1021/ac500968c
Renata Toczyłowska-Mamińska, Andrzej Lewenstam, and Krzysztof Dołowy . Multielectrode Bisensor System for Time-Resolved Monitoring of Ion Transport Across an Epithelial Cell Layer. Analytical Chemistry2014, 86
(1)
, 390-394. https://doi.org/10.1021/ac403808f
Ahmed Ashry, Mohamed Rabia, Sahar Mahmoud Mostafa, Mohamed Ali Korany, Ahmed Ali Farghali, Mohamed Magdy Khalil. β-Cyclodextrin/Zn–Fe layered double hydroxides/graphitic carbon nitride nanomaterials based potentiometric sensor for paroxetine determination in environmental water samples. RSC Advances2024, 14
(47)
, 34791-34803. https://doi.org/10.1039/D4RA03863K
Ashutosh Srivastava, Bholanath Mahanty, Prasanta K. Mohapatra, Debasis Sen, Subir K. Ghosh, Arijit Sengupta, Willem Verboom. Development of a dual sensitive N,N,N’,N’,N”,N”-hexa-n-octylnitrilotriacetamide (HONTA) based potentiometric sensor for direct thorium(IV) estimation. Sensors and Actuators B: Chemical2024, 410 , 135660. https://doi.org/10.1016/j.snb.2024.135660
Lili Gao, Ye Tian, Wenyue Gao, Guobao Xu. Recent Developments and Challenges in Solid-Contact Ion-Selective Electrodes. Sensors2024, 24
(13)
, 4289. https://doi.org/10.3390/s24134289
Valentina M. Keresten, Alexey G. Bykov, Iosif V. Gofman, Elena V. Solovyeva, Andrey Yu Vlasov, Konstantin N. Mikhelson. Non-constancy of the bulk resistance of ionophore-based ion-selective membranes within the Nernstian response range: A semi-quantitative explanation. Journal of Membrane Science2023, 683 , 121830. https://doi.org/10.1016/j.memsci.2023.121830
T. P. Milintha Mary, B. Kumaravel, G. Nagamaniammai, S. Karishma, M. M. Essa, M. W. Qoronfleh, L. Chacko. Biosensors as freshness indicator for packed animal and marine products: A review. International Food Research Journal2023, 30
(4)
, 848-854. https://doi.org/10.47836/ifrj.30.4.03
Gergely T. Solymosi, Róbert E. Gyurcsányi. Understanding the potentiometric response of cation-permselective hydrophilic nanopore-based electrodes in the low ion concentration range. Electrochemistry Communications2023, 153 , 107540. https://doi.org/10.1016/j.elecom.2023.107540
Tlhologelo Lekoane, Phumlani F. Msomi. Quarternized polysulfone/
ZSM
‐5 zeolite composite anion exchange membrane separators for aluminum‐air battery. Journal of Applied Polymer Science2023, 140
(27)
https://doi.org/10.1002/app.54006
Kamonchanok Phoonsawat, Ismail Agir, Wijitar Dungchai, Tugba Ozer, Charles S. Henry. A smartphone-assisted hybrid sensor for simultaneous potentiometric and distance-based detection of electrolytes. Analytica Chimica Acta2022, 1226 , 340245. https://doi.org/10.1016/j.aca.2022.340245
Cesar A. Barbero, María V. Martínez, Diego F. Acevedo, María A. Molina, Claudia R. Rivarola. Cross-Linked Polymeric Gels and Nanocomposites: New Materials and Phenomena Enabling Technological Applications. Macromol2022, 2
(3)
, 440-475. https://doi.org/10.3390/macromol2030028
Jiadi Ying, Yuqing Lin, Yiren Zhang, Yan Jin, Xin Li, Qianhong She, Hideto Matsuyama, Jianguo Yu. Mechanistic insights into the degradation of monovalent selective ion exchange membrane towards long-term application of real salt lake brines. Journal of Membrane Science2022, 652 , 120446. https://doi.org/10.1016/j.memsci.2022.120446
Eliza J. Herrero, Philippe Bühlmann. Potentiometric Sensors with Polymeric Sensing and Reference Membranes Fully Integrated into a Sample‐Wicking Polyester Textile. Analysis & Sensing2021, 1
(4)
, 188-195. https://doi.org/10.1002/anse.202100027
Sahar Mahmoud Mostafa, Ahmed Ali Farghali, Mohamed Magdy Khalil. Novel Zn‐Fe LDH/MWCNT
s
and Graphene/MWCNTs Nanocomposites Based Potentiometric Sensors for Benzydamine Determination in Biological Fluids and Real Water Samples. Electroanalysis2021, 33
(5)
, 1194-1204. https://doi.org/10.1002/elan.202060455
Yujing Liu, Juan Yu, Fan Zhang, Pingang He. All-Solid-State Potentiometric Aptasensing of Streptomycin Based on Signal Amplification by Polycation. IEEE Sensors Journal2021, 21
(5)
, 6300-6305. https://doi.org/10.1109/JSEN.2020.3041305
Canwei Mao, Dajing Yuan, Lu Wang, Eric Bakker. Separating boundary potential changes at thin solid contact ion transfer voltammetric membrane electrodes. Journal of Electroanalytical Chemistry2021, 880 , 114800. https://doi.org/10.1016/j.jelechem.2020.114800
Anca Aldea, Elena Matei, Ricardo J.B. Leote, Ileana Rau, Ionut Enculescu, Victor C. Diculescu. Ionophore- Nafion™ modified gold-coated electrospun polymeric fibers electrodes for determination of electrolytes. Electrochimica Acta2020, 363 , 137239. https://doi.org/10.1016/j.electacta.2020.137239
Rocío Cánovas, Pascal Blondeau, Francisco J. Andrade. Modulating the mixed potential for developing biosensors: Direct potentiometric determination of glucose in whole, undiluted blood. Biosensors and Bioelectronics2020, 163 , 112302. https://doi.org/10.1016/j.bios.2020.112302
Wenyue Gao, Elena Zdrachek, Xiaojiang Xie, Eric Bakker. A Solid‐State Reference Electrode Based on a Self‐Referencing Pulstrode. Angewandte Chemie2020, 132
(6)
, 2314-2318. https://doi.org/10.1002/ange.201912651
Wenyue Gao, Elena Zdrachek, Xiaojiang Xie, Eric Bakker. A Solid‐State Reference Electrode Based on a Self‐Referencing Pulstrode. Angewandte Chemie International Edition2020, 59
(6)
, 2294-2298. https://doi.org/10.1002/anie.201912651
Maral P.S. Mousavi, Mohamed K. Abd El-Rahman, Edward K.W. Tan, Haakon H. Sigurslid, Nooralhuda Arkan, John S. Lane, George M. Whitesides, Philippe Bühlmann. Ionic liquid-based reference electrodes for miniaturized ion sensors: What can go wrong?. Sensors and Actuators B: Chemical2019, 301 , 127112. https://doi.org/10.1016/j.snb.2019.127112
Rafael Hoekstra, Pascal Blondeau, Francisco J. Andrade. IonSens: A Wearable Potentiometric Sensor Patch for Monitoring Total Ion Content in Sweat. Electroanalysis2018, 30
(7)
, 1536-1544. https://doi.org/10.1002/elan.201800128
Miguel Coll Crespi, Gaston A. Crespo, Xiaojiang Xie, Romain Touilloux, Marylou Tercier-Waeber, Eric Bakker. Agarose hydrogel containing immobilized pH buffer microemulsion without increasing permselectivity. Talanta2018, 177 , 191-196. https://doi.org/10.1016/j.talanta.2017.08.053
Carol Korzeniewski, Ying Liang, Pei Zhang, Iqbal Sharif, Jay P. Kitt, Joel M. Harris, Steven J. Hamrock, Stephen E. Creager, Darryl D. DesMarteau. Vibrational Spectroscopy for the Determination of Ionizable Group Content in Ionomer Materials. Applied Spectroscopy2018, 72
(1)
, 141-150. https://doi.org/10.1177/0003702817728243
Anna Nix Davis, Adam R. Travis, Dusty R. Miller, David E. Cliffel. Multianalyte Physiological Microanalytical Devices. Annual Review of Analytical Chemistry2017, 10
(1)
, 93-111. https://doi.org/10.1146/annurev-anchem-061516-045334
Marc Parrilla, Rocío Cánovas, Francisco J. Andrade. Enhanced Potentiometric Detection of Hydrogen Peroxide Using a Platinum Electrode Coated with Nafion. Electroanalysis2017, 29
(1)
, 223-230. https://doi.org/10.1002/elan.201600403
István Makra, Alexandra Brajnovits, Gyula Jágerszki, Péter Fürjes, Róbert E. Gyurcsányi. Potentiometric sensing of nucleic acids using chemically modified nanopores. Nanoscale2017, 9
(2)
, 739-747. https://doi.org/10.1039/C6NR05886H
Lukasz Mendecki, Nicole Callan, Meghan Ahern, Benjamin Schazmann, Aleksandar Radu. Influence of Ionic Liquids on the Selectivity of Ion Exchange-Based Polymer Membrane Sensing Layers. Sensors2016, 16
(7)
, 1106. https://doi.org/10.3390/s16071106
Jinbo Hu, Andreas Stein, Philippe Bühlmann. A Disposable Planar Paper‐Based Potentiometric Ion‐Sensing Platform. Angewandte Chemie2016, 128
(26)
, 7670-7673. https://doi.org/10.1002/ange.201603017
Jinbo Hu, Andreas Stein, Philippe Bühlmann. A Disposable Planar Paper‐Based Potentiometric Ion‐Sensing Platform. Angewandte Chemie International Edition2016, 55
(26)
, 7544-7547. https://doi.org/10.1002/anie.201603017
K N Mikhelson, M A Peshkova. Advances and trends in ionophore-based chemical sensors. Russian Chemical Reviews2015, 84
(6)
, 555-578. https://doi.org/10.1070/RCR4506
Yuri Ermolenko, Dmitrii Kalyagin, Igor Alekseev, Eugene Bychkov, Vasily Kolodnikov, Natalia Melnikova, Igor Murin, Yulia Mourzina, Yuri Vlasov. New membrane material for thallium (I)-selective sensors based on arsenic sulfide glasses. Sensors and Actuators B: Chemical2015, 207 , 940-944. https://doi.org/10.1016/j.snb.2014.07.041
Stéphane Jeanneret, Gastón A. Crespo, Majid Ghahraman Afshar, Eric Bakker. GalvaPot, a custom-made combination galvanostat/potentiostat and high impedance potentiometer for decentralized measurements of ionophore-based electrodes. Sensors and Actuators B: Chemical2015, 207 , 631-639. https://doi.org/10.1016/j.snb.2014.10.084
Majid Ghahraman Afshar, Gastón A. Crespo, Eric Bakker. Counter electrode based on an ion-exchanger Donnan exclusion membrane for bioelectroanalysis. Biosensors and Bioelectronics2014, 61 , 64-69. https://doi.org/10.1016/j.bios.2014.04.039
Gastón A. Crespo, Majid Ghahraman Afshar, Eric Bakker. Chronopotentiometry of pure electrolytes with anion-exchange donnan exclusion membranes. Journal of Electroanalytical Chemistry2014, 731 , 100-106. https://doi.org/10.1016/j.jelechem.2014.08.007
D. S. Kalyagin, Yu. E. Ermolenko, I. E. Alekseev, E. A. Bychkov, S. A. Krotov, N. A. Mel’nikova, I. V. Murin, Yu. G. Vlasov. Ag2S-As2S3-TlI chalcogenide glasses as perspective material for solid-state chemical sensors. Russian Journal of Applied Chemistry2014, 87
(8)
, 1044-1048. https://doi.org/10.1134/S1070427214080060
Andrzej Lewenstam. Routines and Challenges in Clinical Application of Electrochemical Ion‐Sensors. Electroanalysis2014, 26
(6)
, 1171-1181. https://doi.org/10.1002/elan.201400061
Article Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.
The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated.
Figure 1. Potentiometric calibration curves and associated time responses to NaCl additions with the following membranes: (A) FKL (anion-exchange), (B) Nafion, and (C) FAB (both cation-exchange); see Experimental Section.
Figure 2. Potentiometric response of FKL (top) and FAB (bottom) membranes upon exposure to whole blood samples and subsequent standard additions of NaCl.
Figure 3. Repeated external calibrations, each followed by a 30 min exposure to whole blood for the FKL (top) and FAB (bottom) membrane-based ion-selective electrodes.
Salicylate interference with the Roche Cobas Integra chloride electrode. Comments
Mori, Leonard; Waldhuber, Susan
Clinical Chemistry (Washington, D. C.)
(1997),
43
(7),
1249-1250CODEN:
CLCHAU;
ISSN:0009-9147.
(American Association for Clinical Chemistry)
Interference by salicylate on the title electrode leads to abnormally high chloride values which are not found when other brand electrodes are used. Patients showing unexplained high Cl- results on the Integra with a large neg. anion-cation gap should be investigated for salicylate ingestion.
A highly selective, sensitive, fast, and stable amperometric sensor for the detn. of hydrogen peroxide residues in aseptic milk is presented. To fabricate this amperometric sensor, a thin film of Prussian blue was first electrodeposited on a glassy carbon electrode and then a Nafion polymer layer was formed on the top. It was found that Nafion film greatly improves the anti-interference ability and the stability of the Prussian blue-modified electrode. Factors that influence the overall anal. performance of the sensor, such as the concn. of Nafion drop and pH value of the electrolyte, were examd. Results show that the prepd. sensor possesses efficient electrocatalytic activity towards hydrogen peroxide with the detection limit as low as 0.2 μM and linear range from 0.8 μM to 0.12 mM. The developed sensor was applied to the detn. of hydrogen peroxide in milk with satisfactory results.
van der Wal, P. D.; de Rooij, N. F.; Koudelka-Hep, M.Sens. Actuators, B1996, 35, 119–123
17
Extremely stable Nafion based carbon monoxide sensor
van der Wal, P. D.; de Rooij, N. F.; Koudelka-Hep, M.
Sensors and Actuators, B: Chemical
(1996),
35
(1-3),
119-123CODEN:
SABCEB;
ISSN:0925-4005.
(Elsevier)
Carbon monoxide sensors using Nafion solid polymer electrolyte are described. Dry Nafion sensors showed stability problems; on the other hand sensors equipped with a water reservoir (wet Nafion sensors) were extremely stable. The proposed manufg. technol., compatible with hybrid technol. is suitable for cheap mass fabrication.
Mauritz, K. A.; Moore, R. B.Chem. Rev.2004, 104, 4535–4585
21
State of understanding of Nafion
Mauritz, Kenneth A.; Moore, Robert B.
Chemical Reviews (Washington, DC, United States)
(2004),
104
(10),
4535-4585CODEN:
CHREAY;
ISSN:0009-2665.
(American Chemical Society)
A review on morphol. characterization using X-rays and neutrons, microscopy studies, mech. properties, mol. simulations, and the nature of aq. and nonaq. solvents and ions in Nafions.
The structure of the Nafion ionomer used in proton-exchange membranes of H2/O2 fuel cells has long been contentious. Using a recently introduced algorithm, we have quant. simulated previously published small-angle scattering data of hydrated Nafion. The characteristic 'ionomer peak' arises from long parallel but otherwise randomly packed water channels surrounded by partially hydrophilic side branches, forming inverted-micelle cylinders. At 20 vol% water, the water channels have diams. of between 1.8 and 3.5 nm, with an av. of 2.4 nm. Nafion crystallites (∼10 vol%), which form phys. crosslinks that are crucial for the mech. properties of Nafion films, are elongated and parallel to the water channels, with cross-sections of ∼(5 nm)2. Simulations for various other models of Nafion, including Gierke's cluster and the polymer-bundle model, do not match the scattering data. The new model can explain important features of Nafion, including fast diffusion of water and protons through Nafion and its persistence at low temps.
The water-polymer interfacial area per vol., S/V, which is reflected in the Porod region of small-angle scattering data, is an important parameter of different models of the Nafion fuel cell membrane. Therefore, published exptl. S/V data of Nafion are compared over a wide range of hydration levels with various structural models featuring stiff polymer backbones, in particular the parallel water-channel and the polymer ribbon models. The S/V curve at intermediate hydration levels typical of fuel-cell conditions (ca. 20 vol% water) matches that of the parallel water-channel model with mol. corrugation. At higher hydration levels, i.e. for membranes soaked in water or autoclaved at elevated pressures, the polymer-ribbon model matches the decreasing S/V ratio with increasing water content, while the polymer-bundle model predicts a higher surface area. However, the ribbon or bundle models cannot apply at low hydration (< 3 water mols. per Nafion side group), since it is shown that the interfacial area in this regime must increase strongly with hydration, being detd. by the available surface area of the water mols. The pronounced asymmetry of the plot of S/V vs. water vol. fraction is explained in terms of the difference in the diams. of the water mols. and the polymer aggregates.
A new procedure for the detn. of selectivity coeffs. of neutral carrier-based cation-selective electrodes is established that avoids exposure to the preferred ion prior to the measurement of discriminated ions. The method is, therefore, unbiased by the presence of preferred ions in the membrane that otherwise could mask the response to discriminated ion solns. It is generally applicable as long as considerations are met and can only be applied once for a given membrane. Careful studies with sodium-, silver-, and calcium-selective electrodes reveal that Nernstian response slopes can now be obtained for even highly discriminated cations. Specifically, a 1,3-bridged calix[4]arene deriv. as introduced by Yamamoto and Shinkai indeed yields an extraordinary sodium selectivity of log KNa,Kpot = -4.9, with potassium showing Nernst response as well. Analogous measurements with two different silver carriers, a bisthioether-functionalized calix[4]arene and methylenebis(diisobutyldithiocarbamate), and the calcium carrier ETH 129 also show extremely high selectivity, which can satisfactorily be correlated to data obtained previously in ion-buffered solns. The new procedure promises to be a valuable addnl. tool for future characterizations of highly selective ion carriers.
A review, with 29 refs., is given. Selectivities of solvent polymeric membrane ion-selective electrodes (ISEs) are quant. related to equil. at the interface between the sample and the electrode membrane. However, only correctly detd. selectivity coeffs. allow accurate predictions of ISE responses to real-world samples. also, they are also required for the optimization of ionophore structures and membrane compns. Best suited for such purposes are potentiometric selectivity coeffs. as defined already in the 1960s. This paper briefly reviews the basic relations and focuses on possible biases in the detn. of selectivity coeffs. The traditional methods to det. selectivity coeffs. (sep. soln. method, fixed interference method) are still the same as those originally proposed by IUPAC in 1976. However, several precautions are needed to obtain meaningful data. For example, errors arise when the response to a weakly interfering ion is also influenced by the primary ion leaching from the membrane. Wrong selectivity coeffs. may be also obtained when the interfering agent is highly preferred and the electrode shows counterion interference. Recent advances show how such pitfalls can be avoided. A detailed recipe to det. correct potentiometric selectivity coeffs. unaffected by such biases is presented.
Among the published formula for the calcn. of mean activity coeffs., the most reliable and comprehensive are those recently recommended by the National Burea of Stds. In many applications, the ionic strength does not exceed ∼1 M, and the NBS functions can be approximated by a 2-parameter Debye-Hueckel model. The limits of applicability (e.g., 1% deviation from the corresponding NBS model) are listed. The procedure makes efficient use of calculator memory.
The theory of coupled diffusion of multiple ionic species based on complete Donnan exclusion is applied to a diffusion process involving an ion-exchange membrane and three counter ions. The effect of the main process parameters (e.g., diffusion coeffs. and ionic charges) was studied by numerical simulations. The results obtained underline the importance of taking into account the coupled diffusion of all counter ions in a multi-ion system to describe adequately the transport of each individual counter ion.
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.
2025-01-13T22:14:41.906-08:00
Please be aware that pubs.acs.org is undergoing maintenance on Saturday, November 16, at 6 p.m. EDT that may have an impact on your experience. During this time, you may not be able to access certain features like login, purchasing single articles, saving searches or running existing saved searches, modifying your e-Alert preferences, or accessing Librarian administrative functions. We appreciate your patience as we continue to improve the ACS Publications platform.
This website uses cookies to improve your user experience. By continuing to use the site, you are accepting our use of cookies. Read the ACS privacy policy.
