Fast Potentiometric CO2 Sensor for High-Resolution in Situ Measurements in Fresh Water SystemsClick to copy article linkArticle link copied!
- Rohini Athavale*Rohini Athavale*E-mail: [email protected]. Phone Number: +41 587655633.Eawag—Swiss Federal Institute of Aquatic Science and Technology, Department of Surface Waters Research and Management, Seestrasse 79, CH-6047 Kastanienbaum, SwitzerlandInstitute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Universitätsstrasse 16, CH-8092 Zürich, SwitzerlandMore by Rohini Athavale
- Nadezda PankratovaNadezda PankratovaDepartment of Inorganic and Analytical Chemistry, University of Geneva, Quai E.-Ansermet 30, 1211 Geneva, SwitzerlandIntegrated Systems Laboratory (LSI), Swiss Federal Institute of Technology Lausanne (EPFL), CH-1015 Lausanne, SwitzerlandMore by Nadezda Pankratova
- Christian DinkelChristian DinkelEawag—Swiss Federal Institute of Aquatic Science and Technology, Department of Surface Waters Research and Management, Seestrasse 79, CH-6047 Kastanienbaum, SwitzerlandMore by Christian Dinkel
- Eric BakkerEric BakkerDepartment of Inorganic and Analytical Chemistry, University of Geneva, Quai E.-Ansermet 30, 1211 Geneva, SwitzerlandMore by Eric Bakker
- Bernhard WehrliBernhard WehrliEawag—Swiss Federal Institute of Aquatic Science and Technology, Department of Surface Waters Research and Management, Seestrasse 79, CH-6047 Kastanienbaum, SwitzerlandInstitute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Universitätsstrasse 16, CH-8092 Zürich, SwitzerlandMore by Bernhard Wehrli
- Andreas BrandAndreas BrandEawag—Swiss Federal Institute of Aquatic Science and Technology, Department of Surface Waters Research and Management, Seestrasse 79, CH-6047 Kastanienbaum, SwitzerlandInstitute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Universitätsstrasse 16, CH-8092 Zürich, SwitzerlandMore by Andreas Brand
Abstract
We present a new potentiometric sensor principle and a calibration protocol for in situ profiling of dissolved CO2 with high temporal and spatial resolution in fresh water lakes. The sensor system is based on the measurement of EMF between two solid-contact ion selective electrodes (SC-ISEs), a hydrogen ion selective and a carbonate selective sensor. Since it relies on SC-ISEs, it is insensitive to changes in pressure, thus suitable for in situ studies. Also, as it offers a response time (t95%) of <10 s, it allows for profiling applications at high spatial resolution. The proposed optimum in situ protocol accounts for the continuous drift and change in offset that remains a challenge during profiling in natural waters. The fast response resolves features that are usually missed by standard methods like the classical Severinghaus CO2 probe. In addition, the insensitivity of the presented setup to dissolved sulfide allows also for measurements in anoxic zones of eutrophic systems. Highly resolved CO2 concentration profiles obtained by the novel and robust SC-ISE setup along with the developed optimum in situ protocol allow investigating hotspots of biogeochemical processes, such as mineralization and primary production in the water column and help improving estimates for CO2 turnover in freshwater systems.
Introduction



Materials and Methods
Sensor Design
Figure 1
Figure 1. Response (with respective slopes in mV/decade reported in parentheses) of (a) carbonate and hydrogen ion selective SC-ISEs in the laboratory (b) CO2–ISE couples on shipboard (c) CO2–SH probe before the deployment on change in dissolved CO2 concentrations.
Field Site
Set up for in Situ Profiling
Laboratory Analysis
Calculation of Dissolved CO2 Activity
Optimization of Calibration Protocol
(a) different calibration strategiesa | |
---|---|
calibration scheme | description |
1 | shipboard calibration |
2 | in situ calibration; slope value from shipboard calibration; drift and intercept fitted from all sampling points |
3 | in situ calibration; slope value from shipboard calibration; drift and intercept obtained from two (1st and last) sampling points |
4 | in situ calibration, slope value, drift, and intercept obtained from fit to all sampling points |
(b) calibration schemes with corresponding parameters for CO2–ISE couple 1a | |||
---|---|---|---|
calibration type | slope (mV/decade) | intercept (mV) | drift (mV/s) |
1 | 31.06 | –65.36 | — |
2 | 31.06 | –45.94 | 0.005 |
3 | 31.06 | –45.69 | 0.004 |
4 | 32.54 | –38.76 | 0.003 |
(c) calibration schemes with corresponding parameters for CO2–ISE couple 2a | |||
---|---|---|---|
calibration type | slope (mV/decade) | intercept (mV) | drift (mV/s) |
1 | 27.30 | –83.24 | — |
2 | 27.30 | –70.23 | 0.010 |
3 | 27.30 | –68.85 | 0.009 |
4 | 32.82 | –43.46 | 0.003 |
(d) calibration types and parameters for CO2–ISE SH probe | |||
---|---|---|---|
calibration type | slope (mV/decade) | intercept (mV) | drift (mV/s) |
1 | 56.85 | 70.86 | — |
2 | — | — | — |
3 | 56.85 | 98.31 | 0 |
4 | 48.35 | 63.81 | 0 |
Optimal scheme in bold.


Response Time
Results and Discussion
Figure 2
Figure 2. Depth profiles of activity of dissolved CO2 obtained by CO2 ISE couple calculated with different calibration parameters corresponding to the three in situ calibration schemes as described in Table 1. Please note that the dark blue line for calibration scheme 2 is almost overlapped with the light blue line of calibration scheme 4.
Temporal Response
Figure 3
Figure 3. Temporal response of CO2–SH probe and CO2–ISE couple on fast profiling with 5 cm/s (10-fold normal speed). Slopes for both type of sensors as per calibration scheme 3. The blue points on the dissolved oxygen profile and on the depth profile indicate the syringe sampling locations.
Embedded Details in Highly Resolved CO2 Profiles
Figure 4
Figure 4. In situ high-resolution profiles of physicochemical characteristics of water column, activity of dissolved CO2 by CO2–ISE couples and a comparison with simultaneous response of CO2–SH probe and syringe samples at profiling speed 0.5 cm/s in Lake Rotsee.
Supporting Information
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.est.8b02969.
Experimental section with materials and chemicals, sensor fabrication, laboratory tests, sulfide sensitivity test (Figure S1), schemes in optimization of in situ calibration protocol (Figure S2), depth profile of raw and drift corrected ΔEMF (Figure S3), depth profiles of activity of dissolved CO2 obtained by CO2–SH probe with different calibration schemes (Figure S4), in situ profiling set up (Figure S5), selectivity coefficients for ion selective membranes and mean concentrations of relevant ions in the lake water column (Table S1), and performance of SC-ISEs during laboratory tests (Table S2) (PDF)
Terms & Conditions
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.
Acknowledgments
The authors are grateful for the financial support from the Swiss National Science Foundation (SNF Grant 147654). We would like to thank Dajing Yuan for his help in synthesis of f-MWCNTs in the laboratory.
References
This article references 37 other publications.
- 1Raymond, P. A.; Hartmann, J.; Lauerwald, R.; Sobek, S.; McDonald, C.; Hoover, M.; Butman, D.; Striegl, R.; Mayorga, E.; Humborg, C.; Kortelainen, P.; Dürr, H.; Meybeck, M.; Ciais, P.; Guth, P. Global carbon dioxide emissions from inland waters. Nature 2013, 503, 355, DOI: 10.1038/nature12760Google Scholar1https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhvVWntr7K&md5=97da366b6dec9041381ea69d4aa8d9f8Global carbon dioxide emissions from inland watersRaymond, Peter A.; Hartmann, Jens; Lauerwald, Ronny; Sobek, Sebastian; McDonald, Cory; Hoover, Mark; Butman, David; Striegl, Robert; Mayorga, Emilio; Humborg, Christoph; Kortelainen, Pirkko; Duerr, Hans; Meybeck, Michel; Ciais, Philippe; Guth, PeterNature (London, United Kingdom) (2013), 503 (7476), 355-359CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)CO2 transfer from inland waters to the atm., known as CO2 evasion, is a component of the global carbon cycle. Global ests. of CO2 evasion were hampered, however, by the lack of a framework for estg. the inland water surface area and gas transfer velocity and by the absence of a global CO2 database. Here regional variations in global inland water surface area, dissolved CO2, and gas transfer velocity are reported. Global CO2 evasion rates of 1.8 Pg of carbon (Pg C) per yr from streams and rivers and 0.32 Pg C yr-1 from lakes and reservoirs were obtained, where the upper and lower limits are resp. the 5th and 95th confidence interval percentiles. The resulting global evasion rate of 2.1 Pg C yr-1 is higher than previous ests. owing to a larger stream and river evasion rate. The anal. predicts global hotspots in stream and river evasion, with ≈70% of the flux occurring over just 20% of the land surface. The source of inland water CO2 is still not known with certainty and new studies are needed to research the mechanisms controlling CO2 evasion globally.
- 2Milucka, J.; Kirf, M.; Lu, L.; Krupke, A.; Lam, P.; Littmann, S.; Kuypers, M. M. M.; Schubert, C. J. Methane oxidation coupled to oxygenic photosynthesis in anoxic waters. ISME J. 2015, 9, 1991, DOI: 10.1038/ismej.2015.12Google Scholar2https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtl2hs7rK&md5=bebed14eb6c437a513d6b6da68b835e1Methane oxidation coupled to oxygenic photosynthesis in anoxic watersMilucka, Jana; Kirf, Mathias; Lu, Lu; Krupke, Andreas; Lam, Phyllis; Littmann, Sten; Kuypers, Marcel MM; Schubert, Carsten J.ISME Journal (2015), 9 (9), 1991-2002CODEN: IJSOCF; ISSN:1751-7362. (Nature Publishing Group)Freshwater lakes represent large methane sources that, in contrast to the Ocean, significantly contribute to non-anthropogenic methane emissions to the atm. Particularly mixed lakes are major methane emitters, while permanently and seasonally stratified lakes with anoxic bottom waters are often characterized by strongly reduced methane emissions. The causes for this reduced methane flux from anoxic lake waters are not fully understood. Here we identified the microorganisms and processes responsible for the near complete consumption of methane in the anoxic waters of a permanently stratified lake, Lago di Cadagno. Interestingly, known anaerobic methanotrophs could not be detected in these waters. Instead, we found abundant gamma-proteobacterial aerobic methane-oxidizing bacteria active in the anoxic waters. In vitro incubations revealed that, among all the tested potential electron acceptors, only the addn. of oxygen enhanced the rates of methane oxidn. An equally pronounced stimulation was also obsd. when the anoxic water samples were incubated in the light. Our combined results from mol., biogeochem. and single-cell analyses indicate that methane removal at the anoxic chemocline of Lago di Cadagno is due to true aerobic oxidn. of methane fuelled by in situ oxygen prodn. by photosynthetic algae. A similar mechanism could be active in seasonally stratified lakes and marine basins such as the Black Sea, where light penetrates to the anoxic chemocline. Given the widespread occurrence of seasonally stratified anoxic lakes, aerobic methane oxidn. coupled to oxygenic photosynthesis might have an important but so far neglected role in methane emissions from lakes.
- 3Blees, J.; Niemann, H.; Wenk, C. B.; Zopfi, J.; Schubert, C. J.; Kirf, M. K.; Veronesi, M. L.; Hitz, C.; Lehmann, M. F. Micro-aerobic bacterial methane oxidation in the chemocline and anoxic water column of deep south-Alpine Lake Lugano (Switzerland). Limnol. Oceanogr. 2014, 59 (2), 311– 324, DOI: 10.4319/lo.2014.59.2.0311Google Scholar3https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXosVyitbc%253D&md5=70effabb765ba8ff51fb82d9f2063db4Micro-aerobic bacterial methane oxidation in the chemocline and anoxic water column of deep south-Alpine Lake Lugano (Switzerland)Blees, Jan; Niemann, Helge; Wenk, Christine B.; Zopfi, Jakob; Schubert, Carsten J.; Kirf, Mathias K.; Veronesi, Mauro L.; Hitz, Carmen; Lehmann, Moritz F.Limnology and Oceanography (2014), 59 (2), 311-324CODEN: LIOCAH; ISSN:0024-3590. (Association for the Sciences of Limnology and Oceanography, Inc.)We measured seasonal variations in the vertical distribution of methane concn., methane oxidn. rates, and lipid biomarkers in the northern basin of Lake Lugano. Methane consumption below the oxic-anoxic interface co-occurred with concn. maxima of 13C-depleted C16 fatty acid biomarkers (with δ13C values as low as -70‰) in the anoxic water column, as well as characteristic δ13CCH4 profiles. We argue that the conspicuous methane concn. gradients are primarily driven by (micro-)aerobic methane oxidn. (MOx) below the chemocline. We measured a strong MOx potential throughout the anoxic water column, while MOx rates at in situ O2 concn. > 10 nmol L-1 were undetectable. Similarly, we found MOx-related biomarkers and gene sequences encoding the particulate methane monooxygenase in the anoxic, but not the oxic, water. The mechanism of (episodic) oxygen supply sustaining the MOx community in anoxic waters is still uncertain. Our results indicate that a bacterial methanotrophic community is responsible for the methane consumption in Lake Lugano, without detectable contribution from archaeal methanotrophs. Bacterial populations that accumulated both at the suboxic-anoxic interface and in the deeper anoxic hypolimnion, where max. potential MOx rates were obsd. throughout the year (1.5-2.5 μmol L-1 d-1) were mainly related to Methylobacter sp. Close relatives are found in lacustrine environments throughout the world, and their potential to thrive under micro- and anoxic conditions in Lake Lugano may imply that micro-aerobic methane oxidn. is important in methane cycling and competition for methane and oxygen in stratified lakes worldwide.
- 4Wetzel, R. G. The inorganic carbon complex. In Limnology, 3rd ed.; Academic Press: San Diego, CA, 2001; pp 187– 204.Google ScholarThere is no corresponding record for this reference.
- 5Stocker, R. Marine Microbes See a Sea of Gradients. Science 2012, 338 (6107), 628– 633, DOI: 10.1126/science.1208929Google Scholar5https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhsFygtbvE&md5=5345311b56a07384ccbe0bbce591fb19Marine Microbes See a Sea of GradientsStocker, RomanScience (Washington, DC, United States) (2012), 338 (6107), 628-633CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)A review. Marine bacteria influence Earth's environmental dynamics in fundamental ways by controlling the biogeochem. and productivity of the oceans. These large-scale consequences result from the combined effect of countless interactions occurring at the level of the individual cells. At these small scales, the ocean is surprisingly heterogeneous, and microbes experience an environment of pervasive and dynamic chem. and phys. gradients. Many species actively exploit this heterogeneity, while others rely on gradient-independent adaptations. This is an exciting time to explore this frontier of oceanog., but understanding microbial behavior and competition in the context of the water column's microarchitecture calls for new ecol. frameworks, such as a microbial optimal foraging theory, to det. the relevant trade-offs and global consequences of microbial life in a sea of gradients.
- 6Byrne, R. H. Measuring Ocean Acidification: New Technology for a New Era of Ocean Chemistry. Environ. Sci. Technol. 2014, 48 (10), 5352– 5360, DOI: 10.1021/es405819pGoogle Scholar6https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXls1KqsbY%253D&md5=4f1df867ea47c033baecba1ba2f44023Measuring Ocean Acidification: New Technology for a New Era of Ocean ChemistryByrne, Robert H.Environmental Science & Technology (2014), 48 (10), 5352-5360CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)Human addns. of carbon dioxide to the atm. are creating a cascade of chem. consequences that will eventually extend to the bottom of all the world's oceans. Among the best-documented seawater effects are a worldwide increase in open-ocean acidity and large-scale declines in calcium carbonate satn. states. The susceptibility of some young, fast-growing calcareous organisms to adverse impacts highlights the potential for biol. and economic consequences. Many important aspects of seawater CO2 chem. can be only indirectly obsd. at present, and important but difficult-to-observe changes can include shifts in the speciation and possibly bioavailability of some life-essential elements. Innovation and invention are urgently needed to develop the in situ instrumentation required to document this era of rapid ocean evolution.
- 7Abril, G.; Bouillon, S.; Darchambeau, F.; Teodoru, C. R.; Marwick, T. R.; Tamooh, F.; Ochieng Omengo, F.; Geeraert, N.; Deirmendjian, L.; Polsenaere, P.; Borges, A. V. Technical Note: Large overestimation of pCO2 calculated from pH and alkalinity in acidic, organic-rich freshwaters. Biogeosciences 2015, 12 (1), 67– 78, DOI: 10.5194/bg-12-67-2015Google Scholar7https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhsVantrfL&md5=4c83158f0b16066b94207f84aa02ad48Technical note: large overestimation of pCO2 calculated from pH and alkalinity in acidic, organic-rich freshwatersAbril, G.; Bouillon, S.; Darchambeau, F.; Teodoru, C. R.; Marwick, T. R.; Tamooh, F.; Omengo, F. Ochieng; Geeraert, N.; Deirmendjian, L.; Polsenaere, P.; Borges, A. V.Biogeosciences (2015), 12 (1), 67-78CODEN: BIOGGR; ISSN:1726-4189. (Copernicus Publications)Inland waters have been recognized as a significant source of carbon dioxide (CO2) to the atm. at the global scale. Fluxes of CO2 between aquatic systems and the atm. are calcd. from the gas transfer velocity and the water-air gradient of the partial pressure of CO2 (pCO2). Currently, direct measurements of water pCO2 remain scarce in freshwaters, and most published pCO2 data are calcd. from temp., pH and total alky. (TA). Here, we compare calcd. (pH and TA) and measured (equilibrator and headspace) water pCO2 in a large array of temperate and tropical freshwaters. The 761 data points cover a wide range of values for TA (0 to 14 200 μmol L-1), pH (3.94 to 9.17), measured pCO2 (36 to 23 000 ppmv), and dissolved org. carbon (DOC) (29 to 3970 μmol L-1). Calcd. pCO2 were >10% higher than measured pCO2 in 60% of the samples (with a median overestimation of calcd. pCO2 compared to measured pCO2 of 2560 ppmv) and were >100% higher in the 25% most org.-rich and acidic samples (with a median overestimation of 9080 ppmv). We suggest these large overestimations of calcd. pCO2 with respect to measured pCO2 are due to the combination of two cumulative effects: (1) a more significant contribution of org. acids anions to TA in waters with low carbonate alky. and high DOC concns.; (2) a lower buffering capacity of the carbonate system at low pH, which increases the sensitivity of calcd. pCO2 to TA in acidic and organicrich waters. No empirical relationship could be derived from our data set in order to correct calcd. pCO2 for this bias. Owing to the widespread distribution of acidic, org.-rich freshwaters, we conclude that regional and global ests. of CO2 outgassing from freshwaters based on pH and TA data only are most likely overestimated, although the magnitude of the overestimation needs further quant. anal. Direct measurements of pCO2 are recommended in inland waters in general, and in particular in acidic, poorly buffered freshwaters.
- 8Liu, X.; Byrne, R. H.; Adornato, L.; Yates, K. K.; Kaltenbacher, E.; Ding, X.; Yang, B. In Situ Spectrophotometric Measurement of Dissolved Inorganic Carbon in Seawater. Environ. Sci. Technol. 2013, 47 (19), 11106– 11114, DOI: 10.1021/es4014807Google Scholar8https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhtlClsbbE&md5=39af5e62bcfe3ca7dc983f036fba43b7In Situ Spectrophotometric Measurement of Dissolved Inorganic Carbon in SeawaterLiu, Xuewu; Byrne, Robert H.; Adornato, Lori; Yates, Kimberly K.; Kaltenbacher, Eric; Ding, Xiaoling; Yang, BoEnvironmental Science & Technology (2013), 47 (19), 11106-11114CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)Autonomous in situ sensors are needed to document the effects of today's rapid ocean uptake of atm. CO2 (e.g., ocean acidification). General environmental conditions (e.g., biofouling, turbidity) and C-specific conditions (e.g., wide diel variations) present significant challenges to acquiring long-term measurements of dissolved inorg. C (DIC) with satisfactory accuracy and resoln. SEAS-DIC is a new in situ instrument designed to provide calibrated, high-frequency, long-term measurements of DIC in marine and fresh waters. Sample water is 1st acidified to convert all DIC to CO2. The sample and a known reagent soln. are then equilibrated across a gas-permeable membrane. Spectrophotometric measurement of reagent pH can thereby det. the sample DIC over a wide dynamic range, with inherent calibration provided by the pH indicator's mol. characteristics. Field trials indicate that SEAS-DIC performs well in biofouling and turbid waters, with a DIC accuracy and precision of ∼2 μmol/Kg and a measurement rate of ∼1/min. The acidic reagent protects the sensor cell from biofouling, and the gas-permeable membrane excludes particulates from the optical path. This instrument, the 1st spectrophotometric system capable of automated in situ DIC measurements, positions DIC to become a key parameter for in situ CO2-system characterizations.
- 9Wang, Z. A.; Sonnichsen, F. N.; Bradley, A. M.; Hoering, K. A.; Lanagan, T. M.; Chu, S. N.; Hammar, T. R.; Camilli, R. In Situ Sensor Technology for Simultaneous Spectrophotometric Measurements of Seawater Total Dissolved Inorganic Carbon and pH. Environ. Sci. Technol. 2015, 49 (7), 4441– 4449, DOI: 10.1021/es504893nGoogle Scholar9https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXjsVCqurs%253D&md5=2157ec02f0ec262d21bf8d1b70811226In Situ Sensor Technology for Simultaneous Spectrophotometric Measurements of Seawater Total Dissolved Inorganic Carbon and pHWang, Zhaohui Aleck; Sonnichsen, Frederick N.; Bradley, Albert M.; Hoering, Katherine A.; Lanagan, Thomas M.; Chu, Sophie N.; Hammar, Terence R.; Camilli, RichardEnvironmental Science & Technology (2015), 49 (7), 4441-4449CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)A new, in situ sensing system, Channelized Optical System (CHANOS), was recently developed to make high-resoln., simultaneous measurements of total dissolved inorg. carbon (DIC) and pH in seawater. Measurements made by this single, compact sensor can fully characterize the marine carbonate system. The system has a modular design to accommodate two independent, but similar measurement channels for DIC and pH. Both are based on spectrophotometric detection of hydrogen ion concns. The pH channel uses a flow-through, sample-indicator mixing design to achieve near instantaneous measurements. The DIC channel adapts a recently developed spectrophotometric method to achieve flow-through CO2 equilibration between an acidified sample and an indicator soln. with a response time of only ∼90 s. During lab. and in situ testing, CHANOS achieved a precision of ±0.0010 and ±2.5 μmol/kg for pH and DIC, resp. In situ comparison tests indicated that the accuracies of the pH and DIC channels over a three-week time-series deployment were ±0.0024 and ±4.1 μmol/kg, resp. This study demonstrates that CHANOS can make in situ, climatol.-quality measurements by measuring two desirable CO2 parameters, and is capable of resolving the CO2 system in dynamic marine environments.
- 10Martz, T. R.; Dickson, A. G.; DeGrandpre, M. D. Tracer Monitored Titrations: Measurement of Total Alkalinity. Anal. Chem. 2006, 78 (6), 1817– 1826, DOI: 10.1021/ac0516133Google Scholar10https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28XhtlersL0%253D&md5=eb5c1c0e5602498887ab49ce33b0023fTracer Monitored Titrations: Measurement of Total AlkalinityMartz, Todd R.; Dickson, Andrew G.; DeGrandpre, Michael D.Analytical Chemistry (2006), 78 (6), 1817-1826CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)We introduce a new titrn. methodol., tracer monitored titrn. (TMT), in which analyses are free of volumetric and gravimetric measurements and insensitive to pump precision and reproducibility. Spectrophotometric monitoring of titrant diln., rather than vol. increment, lays the burden of anal. performance solely on the spectrophotometer. In the method described here, the titrant is a standardized mixt. of acid-base indicator and strong acid. Diln. of a pulse of titrant in a titrn. vessel is tracked using the total indicator concn. measured spectrophotometrically. The concns. of reacted and unreacted indicator species, derived from Beer's law, are used to calc. the relative proportions of titrant and sample in addn. to the equil. position (pH) of the titrn. mixt. Because the method does not require volumetric or gravimetric addns. of titrant, simple low-precision pumps can be used. Here, we demonstrate application of TMT for detn. of total alky. (AT). High-precision, high-accuracy seawater AT measurements are crucial for understanding, for example, the marine CaCO3 budget and satn. state, anthropogenic CO2 penetration into the oceans, calcareous phytoplankton blooms, and coral reef dynamics. We present data from 286 titrns. on three types of total alky. stds.: Na2CO3 in 0.7 mol/kg ·soln of NaCl, NaOH in 0.7 mol/kg soln NaCl, and a seawater Certified Ref. Material (CRM). Based on Na2CO3 stds., the accuracy and precision are ±0.2 and ±0.1% (4 and 2 μmol/kg soln for AT ∼2100-2500 μmol/kg soln, n = 242), using low-precision solenoid pumps to introduce sample and titrant. Similar accuracy and precision were found for analyses run 42 days after the initial expts. Excellent performance is achieved by optimizing the spectrophotometric detection system and relying upon basic chem. thermodn. for calcg. the equivalence point. Although applied to acid-base titrns. in this paper, the approach should be generally applicable to other types of titrns.
- 11Bell, R. J.; Short, R. T.; Byrne, R. H. In situ determination of total dissolved inorganic carbon by underwater membrane introduction mass spectrometry. Limnol. Oceanogr.: Methods 2011, 9 (4), 164– 175, DOI: 10.4319/lom.2011.9.164Google Scholar11https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXmt1Kms70%253D&md5=e041059b257b71d0857a9dcd3aa93711In situ determination of total dissolved inorganic carbon by underwater membrane introduction mass spectrometryBell, Ryan I.; Short, R. Timothy; Byrne, Robert H.Limnology and Oceanography: Methods (2011), 9 (April), 164-175CODEN: LOMIBY; ISSN:1541-5856. (American Society of Limnology and Oceanography)Procedures have been developed for the detn. of total dissolved inorg. C (DIC) in acidified seawater using an underwater mass spectrometer. Factors affecting the response of the membrane introduction mass spectrometer (MIMS) system were examd. to optimize calibrations and enhance the accuracy of component ocean C system measurements. Lab. studies examd. the following influences on MIMS measurements of DIC: bicarbonate and carbonate contributions to the MIMS CO2 signal intensity, linearity of MIMS response over a wide range of CO2 concns., influence of sample salinity on membrane permeability, and capability to use acidified solns. for calibrations of both DIC and CO2 fugacity. (a) bicarbonate and carbonate contributions to CO2 signal intensity were significant at slow flow rates, (b) MIMS response was linearly dependent on DIC within the concn. range of interest, (c) salinity has a discernable influence on membrane permeability i.e., in turn, dependent on hydrostatic pressure, and (d) well calibrated MIMS measurements for both DIC and CO2 fugacity can be obtained using acidified DIC stds. High flow rates are required during CO2 fugacity measurements in circumneutral seawater to eliminate signal contributions from bicarbonate and carbonate.
- 12Brennwald, M. S.; Schmidt, M.; Oser, J.; Kipfer, R. A Portable and Autonomous Mass Spectrometric System for On-Site Environmental Gas Analysis. Environ. Sci. Technol. 2016, 50 (24), 13455– 13463, DOI: 10.1021/acs.est.6b03669Google Scholar12https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhvFSit7fF&md5=d8b9b0f48c11b27b9d9babeb5ee17b16A Portable and Autonomous Mass Spectrometric System for On-Site Environmental Gas AnalysisBrennwald, Matthias S.; Schmidt, Mark; Oser, Julian; Kipfer, RolfEnvironmental Science & Technology (2016), 50 (24), 13455-13463CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)The authors developed a portable mass spectrometric system (miniRuedi) to quantify He and Ne (in dry gas), and Ar, Kr, N2, O2, CO2, and CH4 partial pressures in gaseous and aq. matrixes in environmental systems with an anal. uncertainty of 1-3%. The miniRuedi does not require purifn. or other prepn. of sampled gas; thus, it allows maintenance-free, autonomous operation. The app. is most suit able for on-site gas anal. during field work and at remote sites due to its small size (60 × 40 × 14 cm), low wt. (13 kg), and low power consumption (50 W). Gases are continuously sampled and transferred through a capillary pressure redn. system into a vacuum chamber where they are analyzed by quadrupole mass spectrometry with a 1-min resoln. time. The low gas consumption rate (<0.1 mL/min) minimizes interference with the gaseous natural mass balance in environmental systems, and allows unbiased quantification of dissolved gas concns. in water by gas/water equilibration using membrane contractors (gas equil./membrane inlet mass spectrometry, GE-MIMS). MiniRuedi performance was demonstrated in lab. and field tests and its utility was illustrated in field applications related to soil gas formation, lake/atm. gas exchange, and seafloor gas emanations.
- 13Kirf, M. K.; Dinkel, C.; Schubert, C. J.; Wehrli, B. Submicromolar Oxygen Profiles at the Oxic–Anoxic Boundary of Temperate Lakes. Aquat. Geochem. 2014, 20 (1), 39– 57, DOI: 10.1007/s10498-013-9206-7Google Scholar13https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXitFChtrk%253D&md5=14bfa750a539f241713953a4641648c4Submicromolar Oxygen Profiles at the Oxic-Anoxic Boundary of Temperate LakesKirf, Mathias K.; Dinkel, Christian; Schubert, Carsten J.; Wehrli, BernhardAquatic Geochemistry (2014), 20 (1), 39-57CODEN: AQGEFP; ISSN:1380-6165. (Springer)Elements involved in biogeochem. cycles undergo rapid turnover at the oxic-anoxic interface of stratified lakes. Here, the presence or absence of oxygen governs abiotic and biotic processes and rates. However, achieving a detailed sampling resoln. to precisely locate the oxic-anoxic interface is difficult due to a lack of fast, drift-free sensors in the working range of 10 to a few 1,000 nmol O2 L-1. Here, we demonstrate that conventional amperometric and optical microsensors can be used to resolve submicromolar oxygen concns. in a continuous profiling mode. The amperometric drift was drastically reduced by anoxic preconditioning. In situ offset correction in the anoxic layer and a high amplification scheme allowed for an excellent detection limit of < 10 nmol L-1. The optical microsensors also showed a similar performance with a detection limit of < 20 nmol L-1. Their drift stability allowed for a lab. calibration in combination with a minor in situ anoxic offset correction. The two different sensor systems showed virtually identical profiles during parallel use in stratified lakes. Both sensors were able to resolve the fine-scale structure at the oxic-anoxic interface and revealed hitherto unnoticed extended zones of submicromolar oxygen concns. even below a steep oxycline. The zones extended up to several meters and showed substantial vertical variability. These results underline the need of a precise localization of the oxic-anoxic interface on a submicromolar scale in order to constrain the relevant aerobic and anaerobic redox processes.
- 14Athavale, R.; Kokorite, I.; Dinkel, C.; Bakker, E.; Wehrli, B.; Crespo, G. A.; Brand, A. In Situ Ammonium Profiling Using Solid-Contact Ion-Selective Electrodes in Eutrophic Lakes. Anal. Chem. 2015, 87 (24), 11990– 11997, DOI: 10.1021/acs.analchem.5b02424Google Scholar14https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhvVGhs7vJ&md5=f45a56ee9162b8e04bddf8fd2018baa4In Situ Ammonium Profiling Using Solid-Contact Ion-Selective Electrodes in Eutrophic LakesAthavale, Rohini; Kokorite, Ilga; Dinkel, Christian; Bakker, Eric; Wehrli, Bernhard; Crespo, Gaston A.; Brand, AndreasAnalytical Chemistry (Washington, DC, United States) (2015), 87 (24), 11990-11997CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)A promising profiling setup for in situ measurements in lakes with potentiometric solid-contact ion-selective electrodes (SC-ISEs) and a data processing method for sensor calibration and drift correction are presented. The profiling setup consists of a logging system, which is equipped with a syringe sampler and sensors for the measurement of std. parameters including temp., cond., O and photosynthetically active radiation (PAR). The setup was expanded with SC-ISEs in galvanically sepd. amplifiers. The potential for high-resoln. profiling is studied by deploying the setup in the eutrophic Lake Rotsee (Lucerne, Switzerland), using 2 different designs of ammonium sensing SC-ISEs. Ammonium was chosen as a target analyte, since it is the most common reduced inorg. N species involved in various pathways of the N cycle and is therefore indicative of numerous biogeochem. processes that occur in lakes such as denitrification and primary prodn. One of the designs, which uses a composite C-nanotube-PVC-based membrane, suffered from sulfide poisoning in the deeper, sulfidic regions of the lake. In contrast, electrodes contg. a plasticizer-free methacrylate copolymer-based sensing layer on top of a conducting polymer layer as a transducer did not show this poisoning effect. The syringe samples drawn during continuous profiling were utilized to calibrate the electrode response. Reaction hotspots and steep gradients of ammonium concns. were identified on-site by monitoring the electrode potential online. Upon conversion to high-resoln. concn. profiles, fine scale features between the calibration points were displayed, which would have been missed by conventional limnol. sampling and subsequent lab. analyses. Thus, the presented setup with SC-ISEs tuned to analytes of interest can facilitate the study of biogeochem. processes that occur at the centimeter scale.
- 15Severinghaus, J. W.; Bradley, A. F. Electrodes for Blood pO2 and pCO2 Determination. J. Appl. Physiol. 1958, 13 (3), 515– 520, DOI: 10.1152/jappl.1958.13.3.515Google Scholar15https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaG1MXmtlWisw%253D%253D&md5=cfba9a07f1c725f87bbee35548b9872fElectrodes for blood pO2 and pCO2 determinationSeveringhaus, John W.; Bradley, A. FreemanJournal of Applied Physiology (1948-1976) (1958), 13 (), 515-20CODEN: JAPYAA; ISSN:0021-8987.Modifications are described in detail of the O electrode of Clark (Trans. Am. Soc. Artificial Internal Organs 2, 41(1956)) and of the CO2 electrode first described by Stow, et al. (C.A. 52, 3006f).
- 16Fietzek, P.; Kötzinger, A. Optimization of a Membrane-Based NDIR Sensor for Dissolved Carbon Dioxide. Proceedings of OceanObs’09: Sustained Ocean Observations and Information for Society, ESA, Publication WPP-306 2010, Venice, Italy, 21–25 September 2009; Hall, J., Harrison, D. E., Stammer, D., Eds.; European Space Agency, 2010.Google ScholarThere is no corresponding record for this reference.
- 17Suzuki, H.; Arakawa, H.; Sasaki, S.; Karube, I. Micromachined Severinghaus-Type Carbon Dioxide Electrode. Anal. Chem. 1999, 71 (9), 1737– 1743, DOI: 10.1021/ac9811468Google Scholar17https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1MXitVagtrc%253D&md5=5a378827b51c05d79424147bc0f8fa87Micromachined Severinghaus-Type Carbon Dioxide ElectrodeSuzuki, Hiroaki; Arakawa, Hiroaki; Sasaki, Satoshi; Karube, IsaoAnalytical Chemistry (1999), 71 (9), 1737-1743CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)The Severinghaus-type pCO2 electrode was miniaturized and batch-fabricated using semiconductor and micromachining techniques. Anodically grown iridium oxide film (AIROF) was employed as the pH sensing element to detect a local pH change caused by the infusion of CO2. The AIROF showed a super-Nernstian response with a slope of ∼-80 mV/pH at 25°. A novel thin-film Ag/AgCl structure was also used. It features a hydrophobic membrane which covers the entire silver layer and the AgCl layer grown from the periphery of the silver pattern. The open-circuit potential of the Ag/AgCl element drifted to the neg. side at -0.1 to -0.2 mV h-1. A microcavity in which the electrolyte soln. was filled was anisotropically etched in a silicon substrate, and a silicone rubber gas-permeable membrane was formed on the sensitive area. The miniature pCO2 electrode showed a distinct response to the variation in concn. of dissolved CO2. The inherent characteristics of the Severinghaus electrode were confirmed in terms of its response and calibration curve. The selectivity of the electrode was satisfactory in view of its application to clin. anal.
- 18Wang, Z. A.; Liu, X.; Byrne, R. H.; Wanninkhof, R.; Bernstein, R. E.; Kaltenbacher, E. A.; Patten, J. Simultaneous spectrophotometric flow-through measurements of pH, carbon dioxide fugacity, and total inorganic carbon in seawater. Anal. Chim. Acta 2007, 596 (1), 23– 36, DOI: 10.1016/j.aca.2007.05.048Google Scholar18https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXnsVKlu7w%253D&md5=4127e6cbdb0c854c23b3639633fef992Simultaneous spectrophotometric flow-through measurements of pH, carbon dioxide fugacity, and total inorganic carbon in seawaterWang, Zhaohui Aleck; Liu, Xuewu; Byrne, Robert H.; Wanninkhof, Rik; Bernstein, Renate E.; Kaltenbacher, Eric A.; Patten, JamesAnalytica Chimica Acta (2007), 596 (1), 23-36CODEN: ACACAM; ISSN:0003-2670. (Elsevier B.V.)An autonomous, multi-parameter, flow-through CO2 system was developed to simultaneously measure surface seawater pH, CO2 fugacity (fCO2), and total dissolved inorg. C (DIC). All 3 measurements are based on spectrophotometric detns. of soln. pH at multiple wavelengths using sulfonephthalein indicators. The pH optical cell was machined from a PEEK (polyetherether ketone) polymer rod bearing a bore-hole with an optical path-length of ∼15 cm. The fCO2 optical cell consists of Teflon AF 2400 (DuPont) capillary tubing sealed in a PEEK rod bore hole. This Teflon AF tubing is filled with a std. indicator soln. with fixed total alky., forming a liq. core wave-guide (LCW). The LCW functions as a long path-length (∼15 cm) optical cell and a membrane which equilibrates the internal std. soln. with external seawater. fCO2 is then detd. by measuring the pH of the internal soln. FCO2 is detd. by measuring the internal soln. pH. DIC is measured by detg. std. internal solns. pH in equil. with seawater which was acidified to convert all forms of DIC to CO2. The system runs repetitive measurement cycles with a sampling frequency of ∼7 samples (21 measurements)/h. It was used to measure surface seawater pH, fCO2, and DIC during the CLIVAR/CO2 A16S cruise in the South Atlantic Ocean, 2005. Field precisions were 0.0008 units for pH, 0.9 μatm for fCO2, and 2.4 μmol/kg for DIC. These field precisions are close to those obtained in the lab. Direct comparison of measurements and measurements obtained using established std. methods showed the system achieved field agreements of 0.0012 ± 0.0042 units for pH, 1.0 ± 2.5 μatm for fCO2, and 2.2 ± 6.0 μmol/kg for DIC. This system integrates spectrophotometric measurements of multiple CO2 parameters into a single package suitable for observations of seawater and freshwater.
- 19Morf, W. E.; Mostert, I. A.; Simon, W. Time response of potentiometric gas sensors to primary and interfering species. Anal. Chem. 1985, 57 (6), 1122– 1126, DOI: 10.1021/ac00283a036Google Scholar19https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL2MXhsF2mtLw%253D&md5=0d55c343fc1f5b3c4fcb06a38a652fc2Time response of potentiometric gas sensors to primary and interfering speciesMorf, Werner E.; Mostert, Irmgard A.; Simon, WilhelmAnalytical Chemistry (1985), 57 (6), 1122-6CODEN: ANCHAM; ISSN:0003-2700.A theor. anal. of the emf. response of gas sensors to interfering gases is presented. The treatment considers the example of CO2 electrodes and analyzes the time and concn. dependence of the interference by acids (HY). The selectivity exhibited by such gas sensors after short measuring periods or at low sample concns. is detd. by the ratio of the permeabilities of the gas-permeable membrane (PHY/PCO2), whereas the final equil. selectivity is given by the ratio of the acidity consts. of the species involved (KHY/KCO2). The predicted time- and concn.-dependent changes in selectivity are in agreement with exptl. findings for different sensor systems. The dynamic response to the primary species CO2 is also treated. The theor. expression derived permits a perfect fit of exptl. time-response curves.
- 20Lopez, M. E. Selectivity of the potentiometric carbon dioxide gas-sensing electrode. Anal. Chem. 1984, 56 (13), 2360– 2366, DOI: 10.1021/ac00277a023Google Scholar20https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL2cXlvVaks78%253D&md5=995da5eb2fd54802538e788fd23d5b82Selectivity of the potentiometric carbon dioxide gas-sensing electrodeLopez, M. E.Analytical Chemistry (1984), 56 (13), 2360-6CODEN: ANCHAM; ISSN:0003-2700.Exptl. and theor. investigations of the potentiometric pCO2 electrode were employed to establish a steady-state model for both org. and inorg. interferences at this electrode. The electrode response is governed primarily by the acidity rather than the volatility of the interferents. With the proposed model, quant. selectivity coeff. values could be calcd. in good agreement with exptl. detd. values.
- 21Athavale, R.; Dinkel, C.; Wehrli, B.; Bakker, E.; Crespo, G. A.; Brand, A. Robust Solid-Contact Ion Selective Electrodes for High-Resolution In Situ Measurements in Fresh Water Systems. Environ. Sci. Technol. Lett. 2017, 4 (7), 286– 291, DOI: 10.1021/acs.estlett.7b00130Google Scholar21https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXnsVWrtrY%253D&md5=a34360ca85238b58dfa03196a110ed01Robust Solid-Contact Ion Selective Electrodes for High-Resolution In Situ Measurements in Fresh Water SystemsAthavale, Rohini; Dinkel, Christian; Wehrli, Bernhard; Bakker, Eric; Crespo, Gaston A.; Brand, AndreasEnvironmental Science & Technology Letters (2017), 4 (7), 286-291CODEN: ESTLCU; ISSN:2328-8930. (American Chemical Society)Biogeochem. processes are often confined to very narrow zones in aquatic systems. Therefore, highly resolved in situ measurements are required to study these processes. Potentiometric solid-contact ion selective electrodes (SC-ISEs) are promising tools for such measurements. SC-ISEs show good performance in analyses under controlled exptl. conditions. Very few sensor designs, however, can sustain the challenges of natural water matrixes and external environmental conditions during in situ applications. We fabricated ammonium and pH selective SC-ISEs with functionalized multiwalled carbon nanotubes (f-MWCNT) as a solid contact. Their functionality was tested in the lab. and applied in situ for vertical profiling in a eutrophic lake. Sensors were insensitive to strong redox changes, high sulfide concns., and bright daylight conditions during the application in the lake. In addn., sensors are easily fabricated and exhibit short response times (<10 s). The proposed design of SC-ISEs based on f-MWCNTs is quite suitable for high-resoln. in situ profiling of ionic species in fresh water lakes.
- 22Xie, X.; Bakker, E. Non-Severinghaus potentiometric dissolved CO2 sensor with improved characteristics. Anal. Chem. 2013, 85 (3), 1332– 6, DOI: 10.1021/ac303534vGoogle Scholar22https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXlt1aqsQ%253D%253D&md5=01984610c75d7e5fe0add123d1a43088Non-Severinghaus Potentiometric Dissolved CO2 Sensor with Improved CharacteristicsXie, Xiaojiang; Bakker, EricAnalytical Chemistry (Washington, DC, United States) (2013), 85 (3), 1332-1336CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)A new type of carbon dioxide sensor comprising a pH glass electrode measured against a carbonate-selective membrane electrode based on a tweezer type carbonate ionophore is presented here for the 1st time. No cumbersome liq. junction based ref. element is used in this measurement. The sensor shows an expected Nernstian divalent response slope to dissolved CO2 over a wide range covering the routine environmental and physiol. PCO2 levels. Unlike the conventional Severinghaus CO2 probe for which the response is substantially delayed to up to 10 min due to diffusion of carbon dioxide into the internal compartment, the ion-selective CO2 sensor proposed here shows a response time (t95%) of 5 s. When used together with a traditional ref. electrode, the sensor system is confirmed to also monitor sample pH and carbonate along with carbon dioxide. A selectivity anal. suggests that Cl- does not interfere even at high concns., allowing one to explore this type of sensor probe for use in seawater or undiluted blood samples. The CO2 probe was used in an aquarium to monitor the CO2 levels caused by the diurnal cycles caused by the metab. of the aquatic plants and shows stable and reproducible results.
- 23Choi, Y. S.; Lvova, L.; Shin, J. H.; Oh, S. H.; Lee, C. S.; Kim, B. H.; Cha, G. S.; Nam, H. Determination of Oceanic Carbon Dioxide Using a Carbonate-Selective Electrode. Anal. Chem. 2002, 74 (10), 2435– 2440, DOI: 10.1021/ac0108459Google Scholar23https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38XivVOis7o%253D&md5=43356d16091688b8bbf6eed043a7c8d6Determination of Oceanic Carbon Dioxide Using a Carbonate-Selective ElectrodeChoi, Yong Suk; Lvova, Larisa; Shin, Jae Ho; Oh, Seong Hee; Lee, Chang Suk; Kim, Byeong Hyo; Cha, Geun Sig; Nam, HakhyunAnalytical Chemistry (2002), 74 (10), 2435-2440CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)Potentiometric properties of PVC membrane-based electrodes prepd. with mol. tweezer-type neutral carriers, 3,12-bis(TFAB)CA and deoxy-3,12-bis(TFAB)CA, and trifluoroacetyl-p-decylbenzene (TFADB) were measured in buffered electrolytes (0.1 M Tris-H2SO4, pH 8.6 and 8.0) and artificial seawater. It was obsd. that deoxy-3,12-bis(TFAB)CA-based electrode provided greatly enhanced CO32- selectivity over Cl- (log KCO32-,Cl-POT ∼-6) and other minor anions present in seawater. Thus, the possibility of applying this carbonate-selective electrode for direct detn. of oceanic CO2 was assessed. Total CO2 (TCO2) concn. in Yellow Sea surface water was detd. with the deoxy-3,12-bis(TFAB)CA-based electrode, Severinghaus-type CO2 gas sensor, and traditional potentiometric titrn. methods. Results showed the carbonate-selective electrode provided accurate oceanic TCO2 detn. comparable to that obtained with the other methods. The anal. procedure based on a carbonate-selective electrode is clearly advantageous over conventional methods; it does not require sample pretreatment or extra reagents other than the std. calibration solns., while providing measured results directly and immediately.
- 24Lee, H. J.; Yoon, I. J.; Yoo, C. L.; Pyun, H.-J.; Cha, G. S.; Nam, H. Potentiometric Evaluation of Solvent Polymeric Carbonate-Selective Membranes Based on Molecular Tweezer-Type Neutral Carriers. Anal. Chem. 2000, 72 (19), 4694– 4699, DOI: 10.1021/ac991212lGoogle Scholar24https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3cXlslOrs7s%253D&md5=10e1d66389bf30b9e692a9ab40e9d954Potentiometric Evaluation of Solvent Polymeric Carbonate-Selective Membranes Based on Molecular Tweezer-Type Neutral CarriersLee, Han Jin; Yoon, In Joon; Yoo, Choong Leol; Pyun, Hyung-Jung; Cha, Geun Sig; Nam, HakhyunAnalytical Chemistry (2000), 72 (19), 4694-4699CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)Potentiometric properties of the ion-selective electrodes based on highly plasticized PVC membranes doped with the carbonate-selective cholic acid (CA) derivs. have been measured. The carbonate-selective neutral carriers have been prepd. by coupling one to three trifluoroacetobenzoyl (TFAB) groups to a cholic acid deriv. which has three hydroxyl linkers lining on the C3, C7, and C12 positions of its rigid steroidal ring structure. The membranes based on cholic acid derivs. with two TFABs [3,7-bis(TFAB)CA, 3,12-bis(TFAB)CA, and 7,12-bis(TFAB)CA] exhibited remarkably improved carbonate selectivity, indicating that the bis(TFAB)CAs behave like mol. tweezers for the carbonate ion. For example, 3,12-bis(TFAB)CA resulted in 10-300-fold-enhanced carbonate selectivity over other anions (e.g., salicylate, ClO4-, SCN-, HPO42-, NO3-, NO2-, Br-, and Cl-) compared to that of the neutral carriers with a single TFAB group. The distances between the carbonate binding centers of bis(TFAB)CAs, i.e., the carbonyl carbons of the two TFAB groups, are in the 7.3-7.9-Å range at the AM1 level semiempirical calcn., which is too far for the carbonate ion to form direct covalent bonding. The fast atom bombardment mass spectra of bis(TFAB)CAs show that significant fractions of the compds. are either mono- or dihydrated before complexing the carbonate ion. These findings seem to suggest that bis(TFAB)CAs recognize the incoming carbonate ion by forming both covalent and hydrogen bonding between the hydrated and unhydrated TFAB groups. The anal. utility of the carbonate-selective electrode based on 3,12-bis(TFAB)CA has been demonstrated by measuring the total carbon dioxide in human serum in the presence of lipophilic anion interferents, e.g., salicylate.
- 25de Beer, D.; Bissett, A.; de Wit, R.; Jonkers, H.; Köhler-Rink, S.; Nam, H.; Kim, B. H.; Eickert, G.; Grinstain, M. A microsensor for carbonate ions suitable for microprofiling in freshwater and saline environments. Limnol. Oceanogr.: Methods 2008, 6 (10), 532– 541, DOI: 10.4319/lom.2008.6.532Google Scholar25https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXhtVWqs77P&md5=8074d39543be457386550b77716ca2ccA microsensor for carbonate ions suitable for microprofiling in freshwater and saline environmentsde Beer, Dirk; Bissett, Andrew; de Wit, Rutger; Jonkers, Henk; Koehler-Rink, Stefanie; Nam, Hakyun; Kim, Byeong Hyo; Eickert, Gabriele; Grinstain, MorLimnology and Oceanography: Methods (2008), 6 (Oct.), 532-541CODEN: LOMIBY; ISSN:1541-5856. (American Society of Limnology and Oceanography)A novel carbonate microsensor, based on the ion-selective ionophore N,N,-dioctyl-3α, 12 α-bis(4-trifluoroacetylbenzoxy)-5β-cholan-24-amide, is presented. The sensor chem. and filling electrolyte, used previously for macrosensors, was improved for use in microsensors, and a simple calibration procedure was designed. The sensor is highly selective for carbonate, having a similar selectivity as the macrosensor, and is so insensitive to Cl- interference that it can be used in seawater. The ability to measure accurate profiles with the carbonate sensor was verified in agar gels with artificial carbonate gradients. Several environmental applications are presented, including photosynthesis and calcification measurements in freshwater stromatolites (tufas) and foraminifera. Carbonate profiles in illuminated and darkened hypersaline microbial mats were qual. as expected and aligned with the oxygen and pH profiles. The dissolved inorg. carbon profiles calcd. from local pH and carbonate values, however, did not follow the expected trends, both in the foraminifera and the hypersaline mat. Temporal and spatial heterogeneities make perfect alignment of pH and carbonate profiles, needed for DIC calcns., unrealistic. The calcn. of dissolved inorg. carbon microprofiles from pH and carbonate microprofiles is not recommended. The microsensor is highly useful in studies on calcification and decalcification, where direct concns. of carbonate and calcium ions are needed.
- 26Pankratova, N.; Crespo, G. A.; Afshar, M. G.; Crespi, M. C.; Jeanneret, S.; Cherubini, T.; Tercier-Waeber, M.-L.; Pomati, F.; Bakker, E. Potentiometric sensing array for monitoring aquatic systems. Environ. Sci.: Processes Impacts 2015, 17 (5), 906– 914, DOI: 10.1039/C5EM00038FGoogle Scholar26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXlt1ant7o%253D&md5=f93820ee32f7fdf68f4dd790540b51d4Potentiometric sensing array for monitoring aquatic systemsPankratova, Nadezda; Crespo, Gaston A.; Afshar, Majid Ghahraman; Crespi, Miquel Coll; Jeanneret, Stephane; Cherubini, Thomas; Tercier-Waeber, Mary-Lou; Pomati, Francesco; Bakker, EricEnvironmental Science: Processes & Impacts (2015), 17 (5), 906-914CODEN: ESPICZ; ISSN:2050-7895. (Royal Society of Chemistry)Since aquatic environments are highly heterogeneous and dynamic, there is the need in aquatic ecosystem monitoring to replace traditional approaches based on periodical sampling followed by lab. anal. with new automated techniques that allow one to obtain monitoring data with high spatial and temporal resoln. We report here on a potentiometric sensing array based on polymeric membrane materials for the continuous monitoring of nutrients and chem. species relevant for the carbon cycle in freshwater ecosystems. The proposed setup operates autonomously, with measurement, calibration, fluidic control and acquisition triggers all integrated into a self-contained instrument. Exptl. validation was performed on an automated monitoring platform on lake Greifensee (Switzerland) using potentiometric sensors selective for hydrogen ions, carbonate, calcium, nitrate and ammonium. Results from the field tests were compared with those obtained by traditional lab. anal. A linear correlation between calcium and nitrate activities measured with ISEs and relevant concns. measured in the lab. was found, with the slopes corresponding to apparent single ion activity coeffs. [Formula Omitted] and [Formula Omitted]. Good correlation between pH values measured with ISE and CTD probes (SD = 0.2 pH) suggests adequate reliability of the methodol.
- 27Yuan, D.; Anthis, A. H. C.; Ghahraman Afshar, M.; Pankratova, N.; Cuartero, M.; Crespo, G. A.; Bakker, E. All-Solid-State Potentiometric Sensors with a Multiwalled Carbon Nanotube Inner Transducing Layer for Anion Detection in Environmental Samples. Anal. Chem. 2015, 87 (17), 8640– 8645, DOI: 10.1021/acs.analchem.5b01941Google Scholar27https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtlemurjO&md5=e0484a7b9d636d491402bcfb9953cd7cAll-Solid-State Potentiometric Sensors with a Multiwalled Carbon Nanotube Inner Transducing Layer for Anion Detection in Environmental SamplesYuan, Dajing; Anthis, Alexandre H. C.; Ghahraman Afshar, Majid; Pankratova, Nadezda; Cuartero, Maria; Crespo, Gaston A.; Bakker, EricAnalytical Chemistry (Washington, DC, United States) (2015), 87 (17), 8640-8645CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)While ion to electron transducing layers for the fabrication of potentiometric membrane electrodes for the detection of cations were well established, similar progress for the sensing of anions has not yet been realized. The authors report for this reason on a novel approach for the development of all-solid-state anion selective electrodes using lipophilic multiwalled carbon nanotubes (f-MWCNTs) as the inner ion to electron transducing layer. This material can be solvent cast, as it conveniently dissolves in THF, an important advantage to develop uniform films without the need for using surfactants that might deteriorate the performance of the electrode. Solid contact sensors for carbonate, nitrate, nitrite, and dihydrogen phosphate are fabricated and characterized, and all exhibit comparable anal. characteristics to the inner liq. electrodes. For example, the carbonate sensor exhibits a Nernstian slope of 27.2 ± 0.8 mV dec-1, a LOD = 2.3 μM, a response time of 1 s, a linear range of four logarithmic units, and a medium-term stability of 0.04 mV h-1 was obtained in a pH 8.6 buffered soln. Water layer test, reversibility, and selectivity for chloride, nitrate, and hydroxide are also reported. The excellent properties of f-MWCNTs as a transducer are contrasted to the deficient performance of poly(3-octyl-thiophene) (POT) for carbonate detection. This is evidenced both with a significant drift in the potentiometric measures as well as a pronounced sensitivity to light (either sunlight or artificial light). This latter aspect may compromise its potential for environmental in situ measurements (night/day cycles). The concn. of carbonate is detd. in a river sample (Arve river, Geneva) and compared to a ref. method (automatic titrator with potentiometric pH detection). Probably nanostructured materials such as f-MWCNTs are an attractive platform as a general ion-to-electron transducer for anion-selective electrodes.
- 28Brand, A.; Bruderer, H.; Oswald, K.; Guggenheim, C.; Schubert, C. J.; Wehrli, B. Oxygenic primary production below the oxycline and its importance for redox dynamics. Aquat. Sci. 2016, 78 (4), 727– 741, DOI: 10.1007/s00027-016-0465-4Google Scholar28https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XitVOntrc%253D&md5=523289ceef04015d613a2cb46964de51Oxygenic primary production below the oxycline and its importance for redox dynamicsBrand, Andreas; Bruderer, Hannah; Oswald, Kirsten; Guggenheim, Carole; Schubert, Carsten J.; Wehrli, BernhardAquatic Sciences (2016), 78 (4), 727-741CODEN: AQSCEA; ISSN:1015-1621. (Birkhaeuser Basel)We present evidence that oxygenic primary prodn. occurs in the virtually anoxic regions (i.e. regions where no oxygen was detected) of the eutrophic, pre-alpine Lake Rot (Switzerland). Chlorophyll-a measurements in combination with phytoplankton densities indicated the presence of oxygenic primary producers throughout the water column. While Chlorophyceae were present as the main class of oxygenic phototrophs above the oxycline, which extended from 8 down to 9.2 m, the phototrophic community in and below the oxycline was dominated by cyanobacteria. In-situ incubation expts. with H14CO3- conducted in August 2013 revealed an oxygenic primary prodn. rate of 1.0 and 0.5 mg C m-3 h-1 in 9 and 10 m depth, resp. However, measurements with optical trace oxygen sensors showed that oxygen concns. were below the detection limit (20 nmol l-1) during the incubation period below 9.2 m. Potential oxygen consumption rates, which were 10-20 times higher than oxygen prodn. rates, explain this absence of free oxygen. Our data show that oxygen prodn. in the virtually anoxic zone corresponded to approx. 8 % of the oxygen flux driven by the concn. gradient in the oxycline. This provided an important source of electron acceptors for biogeochem. processes beyond the conventional redox boundary and in the apparently oxygen depleted zone of Lake Rot. This oxygenic primary prodn. in the virtually anoxic zone could allow growth and activity of aerobic microorganisms adapted to low oxygen supply.
- 29Müller, B.; Maerki, M.; Dinkel, C.; Stierli, R.; Wehrli, B. In Situ Measurements in Lake Sediments Using Ion-Selective Electrodes with a Profiling Lander System. In Environmental Electrochemistry; American Chemical Society, 2002; Vol. 811, pp 126– 143.Google ScholarThere is no corresponding record for this reference.
- 30Cline, J. D. Spectrophotometric determination of hydrogen sulfide in natural waters. Limnol. Oceanogr. 1969, 14 (3), 454– 458, DOI: 10.4319/lo.1969.14.3.0454Google Scholar30https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaF1MXksFegu70%253D&md5=d7e10415590a7dd4dc2e1c4c3896a0dbSpectrophotometric determination of hydrogen sulfide in natural watersCline, Joel D.Limnology and Oceanography (1969), 14 (3), 454-8CODEN: LIOCAH; ISSN:0024-3590.To det. dissolved H2S (H2S, HS-, S2-) in the concn. range of 1-1,000 μg./l., a mixed diamine reagent is used which is prepd. by dissolving 0.5-20 g. (depending on sulfide concn.) of N,N-dimethyl-p-phenylenediamine sulfate and FeCl3.6H2O (0.75-30.0 g. depending on sulfide concn.) in 500 ml. of cool 50% reagent grade HCl. In sulfide concn. in μmoles/l. is 1-3, the amt. of diamine is 0.5 g. and the Fe(III) is 0.75 g.; at 3-40, the diamine is 2.0 and Fe is 3.0; at 40-250 diamine is 8.0 and Fe is 12.0; at 250-1000 the diamine level is 20.0 and the Fe is 30.0. Exptl. a 50-ml. sample is transferred from the syringe to a 50-ml. serum bottle, to which 4 ml. of the appropriate mixed diamine reagent is added. A 5-ml. syringe with a 4-ml. stop position is satisfactory for reagent delivery. The serum cap is replaced promptly to reduce volatilization of the H2S and the soln. is mixed gently. After 20 min. the absorbance is detd. spectrophotometrically at 670 mμ in the appropriate cuvette. All necessary dilns. should be made after the color development time and in volumetric glassware. Diln. factors and path lengths are recommended for best results. Standardization is described and sensitivity, precision, and accuracy are detd. Temp. effect and interferences are discussed.
- 31Parkhurst, D. L. User’s Guide to PHREEQC: A Computer Program for Speciation, Reaction-Path, Advective-Transport, and Inverse Geochemical Calculations; U.S. Dept. of the Interior, U.S. Geological Survey: Denver, CO, 1995. https://search.library.wisc.edu/catalog/999778194102121.Google ScholarThere is no corresponding record for this reference.
- 32Crespo, G. A.; Gugsa, D.; Macho, S.; Rius, F. X. Solid-contact pH-selective electrode using multi-walled carbon nanotubes. Anal. Bioanal. Chem. 2009, 395 (7), 2371– 2376, DOI: 10.1007/s00216-009-3127-8Google Scholar32https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXhtFCnsrbN&md5=1640f851ca344ced4991fb8b25a47c3eSolid-contact pH-selective electrode using multi-walled carbon nanotubesCrespo, Gaston A.; Gugsa, Derese; Macho, Santiago; Rius, F. XavierAnalytical and Bioanalytical Chemistry (2009), 395 (7), 2371-2376CODEN: ABCNBP; ISSN:1618-2642. (Springer)Multi-walled C nanotubes (MWCNT) are efficient transducers of the ionic-to-electronic current. This enables the development of a new solid-contact pH-selective electrode that is based on the deposition of a 35-μm thick layer of MWCNT between the acrylic ion-selective membrane and the glassy C rod used as the elec. conductor. The ion-selective membrane was prepd. by incorporating tridodecylamine as the ionophore, K tetrakis[3,5-bis(trifluoromethyl)phenyl]borate as the lipophilic additive in a polymd. methylmethacrylate and an Bu acrylate matrix. The potentiometric response shows Nernstian behavior and a linear dynamic range between 2.89 and 9.90 pH values. The response time for this electrode was <10 s throughout the whole working range. The electrode shows a high selectivity towards interfering ions. Electrochem. impedance spectroscopy and chronopotentiometry techniques were used to characterize the electrochem. behavior and the stability of the C-nanotube-based ion-selective electrodes.
- 33Fibbioli, M.; Bandyopadhyay, K.; Liu, S.-G.; Echegoyen, L.; Enger, O.; Diederich, F.; Buhlmann, P.; Pretsch, E. Redox-active self-assembled monolayers as novel solid contacts for ion-selective electrodes. Chem. Commun. 2000, (5), 339– 340, DOI: 10.1039/a909532bGoogle Scholar33https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3cXhtlenu7o%253D&md5=df7b52db4206332b5fe02f40d357eb40Redox-active self-assembled monolayers as novel solid contacts for ion-selective electrodesFibbioli, Monia; Enger, Olivier; Diederich, Francois; Pretsch, Erno; Bandyopadhyay, Krisanu; Liu, Sheng-Gao; Echegoyen, Luis; Buhlmann, PhilippeChemical Communications (Cambridge) (2000), (5), 339-340CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)A new methodol. to fabricate solid-contact ion-selective electrodes (SC-ISEs) using SAMs of a lipophilic redox-active compd. to facilitate the charge transfer across the interface leads to improved potential stability and prevents redox or O2 interference of valinomycin-based SC-ISEs.
- 34Lindner, E.; Gyurcsanyi, R. E. Quality control criteria for solid-contact, solvent polymeric membrane ion-selective electrodes. J. Solid State Electrochem. 2009, 13 (1), 51– 68, DOI: 10.1007/s10008-008-0608-1Google Scholar34https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXht1Knu7zI&md5=953a27fe92b19acc3301ad2f9493c3bfQuality control criteria for solid-contact, solvent polymeric membrane ion-selective electrodesLindner, Erno; Gyurcsanyi, Robert E.Journal of Solid State Electrochemistry (2009), 13 (1), 51-68CODEN: JSSEFS; ISSN:1432-8488. (Springer GmbH)A review. After a long history and conflicting views, solid-contact (SC) solvent polymeric membrane ion-selective electrodes (ISEs) emerged as reliable potentiometric-sensing devices with unique advantages. From the large variety of proposed SCs inherently conductive polymers emerged as the materials of choice. In the view, the most attractive feature of SC ISEs is their compatibility with thin- and thick-film micro-fabrication technologies that can provide cheap, mass-produced sensors and sensor arrays that can be integrated with the measuring, data acquisition, and control electronics in a straightforward way. However, despite the impressive properties of certain SC electrodes and their potential advantages, they remained primarily in the research labs. To make the jump from the research labs. into com. devices, it would be essential to prove that miniaturized SC ISEs can indeed match or surpass the performance characteristics of the conventional, liq.-contact macro-electrodes. It would be important to settle on the quality control criteria and testing protocols for assessing the performance characteristics of SC electrodes. It could help in interpreting the sometimes-inconsistent exptl. data. Once cheap, miniaturized, SC ISEs will match the performance characteristics of macroscopic-size electrodes, it is expected to have an important impact in a variety of applications requiring robust, maintenance-free, or single-use ISEs, e.g., in home care or bedside diagnostics, environmental anal., and quality control assessment. Reliable SC ISEs are expected to revitalize the field of ion-selective field effect transistors and open new possibilities in combination with nanowire-based devices.
- 35Mousavi, Z.; Teter, A.; Lewenstam, A.; Maj-Zurawska, M.; Ivaska, A.; Bobacka, J. Comparison of Multi-walled Carbon Nanotubes and Poly(3-octylthiophene) as Ion-to-Electron Transducers in All-Solid-State Potassium Ion-Selective Electrodes. Electroanalysis 2011, 23 (6), 1352– 1358, DOI: 10.1002/elan.201000747Google Scholar35https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXmvFCnt7o%253D&md5=bfaa4343fbea256f7946ea8bbf9a134aComparison of multi-walled carbon nanotubes and poly(3-octylthiophene) as ion-to-electron transducers in all-solid-state potassium ion-selective electrodesMousavi, Zekra; Teter, Agnieszka; Lewenstam, Andrzej; Maj-Zurawska, Magdalena; Ivaska, Ari; Bobacka, JohanElectroanalysis (2011), 23 (6), 1352-1358CODEN: ELANEU; ISSN:1040-0397. (Wiley-VCH Verlag GmbH & Co. KGaA)Multi-walled carbon nanotubes (MWCNTs) were compared with poly(3-octylthiophene) (POT) as ion-to-electron transducer in all-solid-state potassium ion-selective electrodes with valinomycin-based ion-selective membranes. MWCNTs and POT were mixed with the other components of the potassium ion-selective membrane cocktail (valinomycin, KTpClPB, o-NPOE, PVC, THF) which was then applied on a glassy carbon (GC) substrate to prep. single-piece ion-selective electrodes (SPISEs). Results from potentiometric and impedance measurements showed that the MWCNT-based electrodes have a more reproducible std. potential and a lower overall impedance than the electrodes based on POT. Both types of electrodes showed similar sensitivity to K+ and no redox sensitivity.
- 36Lindner, E.; Toth, K.; Pungor, E. Definition and determination of response time of ion selective electrodes. Pure Appl. Chem. 1986, 58 (3), 469– 479, DOI: 10.1351/pac198658030469Google Scholar36https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL28XitlKhtL4%253D&md5=15ceb89406c61c46f83646796d71de7cDefinition and determination of response time of ion selective electrodesLindner, E.; Toth, Klara; Pungor, E.Pure and Applied Chemistry (1986), 58 (3), 469-79CODEN: PACHAS; ISSN:0033-4545.A review with 30 refs. The topics include: concept of response time, detn. of response time, limits of the activity step method, definition of response time, and comparison of response time data calcd. according to different math. models and response time definitions.
- 37Oswald, K.; Milucka, J.; Brand, A.; Littmann, S.; Wehrli, B.; Kuypers, M. M. M.; Schubert, C. J. Light-Dependent Aerobic Methane Oxidation Reduces Methane Emissions from Seasonally Stratified Lakes. PLoS One 2015, 10 (7), e0132574 DOI: 10.1371/journal.pone.0132574Google Scholar37https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhsV2rt7fI&md5=f49d5a6c069f047e0f33eaa5aee5b0acLight-dependent aerobic methane oxidation reduces methane emissions from seasonally stratified lakesOswald, Kirsten; Milucka, Jana; Brand, Andreas; Littmann, Sten; Wehrli, Bernhard; Kuypers, Marcel M. M.; Schubert, Carsten J.PLoS One (2015), 10 (7), e0132574/1-e0132574/22CODEN: POLNCL; ISSN:1932-6203. (Public Library of Science)Lakes are a natural source of methane to the atm. and contribute significantly to total emissions compared to the oceans. Controls on methane emissions from lake surfaces, particularly biotic processes within anoxic hypolimnia, are only partially understood. Here we investigated biol. methane oxidn. in the water column of the seasonally stratified Lake Rotsee. A zone of methane oxidn. extending from the oxic/anoxic interface into anoxic waters was identified by chem. profiling of oxygen, methane and δ13C of methane. Incubation expts. with 13C-methane yielded highest oxidn. rates within the oxycline, and comparable rates were measured in anoxic waters. Despite predominantly anoxic conditions within the zone of methane oxidn., known groups of anaerobic methanotrophic archaea were conspicuously absent. Instead, aerobic gammaproteobacterial methanotrophs were identified as the active methane oxidizers. In addn., continuous oxidn. and max. rates always occurred under light conditions. These findings, along with the detection of chlorophyll a, suggest that aerobic methane oxidn. is tightly coupled to light-dependent photosynthetic oxygen prodn. both at the oxycline and in the anoxic bottom layer. It is likely that this interaction between oxygenic phototrophs and aerobic methanotrophs represents a widespread mechanism by which methane is oxidized in lake water, thus diminishing its release into the atm.
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- Shuangqing Mu, Tanji Yin, Feng Luan, Wei Qin. High-redox-capacity solid contact based on ferrocenyl self-assembled monolayer functionalized macroporous gold for an all-solid-state carbonate-selective electrode. Microchemical Journal 2024, 197 , 109696. https://doi.org/10.1016/j.microc.2023.109696
- Regina Belugina, Elena Puchkova, Ekaterina Yuskina, Arsen Khalatov, Vladimir Podberezskiy, Sergey Savinov, Andrey Legin, Vitaly Panchuk, Dmitry Kirsanov. Getting rid of reference electrode in potentiometric multisensor measurements. Sensors and Actuators B: Chemical 2023, 393 , 134269. https://doi.org/10.1016/j.snb.2023.134269
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Abstract
Figure 1
Figure 1. Response (with respective slopes in mV/decade reported in parentheses) of (a) carbonate and hydrogen ion selective SC-ISEs in the laboratory (b) CO2–ISE couples on shipboard (c) CO2–SH probe before the deployment on change in dissolved CO2 concentrations.
Figure 2
Figure 2. Depth profiles of activity of dissolved CO2 obtained by CO2 ISE couple calculated with different calibration parameters corresponding to the three in situ calibration schemes as described in Table 1. Please note that the dark blue line for calibration scheme 2 is almost overlapped with the light blue line of calibration scheme 4.
Figure 3
Figure 3. Temporal response of CO2–SH probe and CO2–ISE couple on fast profiling with 5 cm/s (10-fold normal speed). Slopes for both type of sensors as per calibration scheme 3. The blue points on the dissolved oxygen profile and on the depth profile indicate the syringe sampling locations.
Figure 4
Figure 4. In situ high-resolution profiles of physicochemical characteristics of water column, activity of dissolved CO2 by CO2–ISE couples and a comparison with simultaneous response of CO2–SH probe and syringe samples at profiling speed 0.5 cm/s in Lake Rotsee.
References
This article references 37 other publications.
- 1Raymond, P. A.; Hartmann, J.; Lauerwald, R.; Sobek, S.; McDonald, C.; Hoover, M.; Butman, D.; Striegl, R.; Mayorga, E.; Humborg, C.; Kortelainen, P.; Dürr, H.; Meybeck, M.; Ciais, P.; Guth, P. Global carbon dioxide emissions from inland waters. Nature 2013, 503, 355, DOI: 10.1038/nature127601https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhvVWntr7K&md5=97da366b6dec9041381ea69d4aa8d9f8Global carbon dioxide emissions from inland watersRaymond, Peter A.; Hartmann, Jens; Lauerwald, Ronny; Sobek, Sebastian; McDonald, Cory; Hoover, Mark; Butman, David; Striegl, Robert; Mayorga, Emilio; Humborg, Christoph; Kortelainen, Pirkko; Duerr, Hans; Meybeck, Michel; Ciais, Philippe; Guth, PeterNature (London, United Kingdom) (2013), 503 (7476), 355-359CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)CO2 transfer from inland waters to the atm., known as CO2 evasion, is a component of the global carbon cycle. Global ests. of CO2 evasion were hampered, however, by the lack of a framework for estg. the inland water surface area and gas transfer velocity and by the absence of a global CO2 database. Here regional variations in global inland water surface area, dissolved CO2, and gas transfer velocity are reported. Global CO2 evasion rates of 1.8 Pg of carbon (Pg C) per yr from streams and rivers and 0.32 Pg C yr-1 from lakes and reservoirs were obtained, where the upper and lower limits are resp. the 5th and 95th confidence interval percentiles. The resulting global evasion rate of 2.1 Pg C yr-1 is higher than previous ests. owing to a larger stream and river evasion rate. The anal. predicts global hotspots in stream and river evasion, with ≈70% of the flux occurring over just 20% of the land surface. The source of inland water CO2 is still not known with certainty and new studies are needed to research the mechanisms controlling CO2 evasion globally.
- 2Milucka, J.; Kirf, M.; Lu, L.; Krupke, A.; Lam, P.; Littmann, S.; Kuypers, M. M. M.; Schubert, C. J. Methane oxidation coupled to oxygenic photosynthesis in anoxic waters. ISME J. 2015, 9, 1991, DOI: 10.1038/ismej.2015.122https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtl2hs7rK&md5=bebed14eb6c437a513d6b6da68b835e1Methane oxidation coupled to oxygenic photosynthesis in anoxic watersMilucka, Jana; Kirf, Mathias; Lu, Lu; Krupke, Andreas; Lam, Phyllis; Littmann, Sten; Kuypers, Marcel MM; Schubert, Carsten J.ISME Journal (2015), 9 (9), 1991-2002CODEN: IJSOCF; ISSN:1751-7362. (Nature Publishing Group)Freshwater lakes represent large methane sources that, in contrast to the Ocean, significantly contribute to non-anthropogenic methane emissions to the atm. Particularly mixed lakes are major methane emitters, while permanently and seasonally stratified lakes with anoxic bottom waters are often characterized by strongly reduced methane emissions. The causes for this reduced methane flux from anoxic lake waters are not fully understood. Here we identified the microorganisms and processes responsible for the near complete consumption of methane in the anoxic waters of a permanently stratified lake, Lago di Cadagno. Interestingly, known anaerobic methanotrophs could not be detected in these waters. Instead, we found abundant gamma-proteobacterial aerobic methane-oxidizing bacteria active in the anoxic waters. In vitro incubations revealed that, among all the tested potential electron acceptors, only the addn. of oxygen enhanced the rates of methane oxidn. An equally pronounced stimulation was also obsd. when the anoxic water samples were incubated in the light. Our combined results from mol., biogeochem. and single-cell analyses indicate that methane removal at the anoxic chemocline of Lago di Cadagno is due to true aerobic oxidn. of methane fuelled by in situ oxygen prodn. by photosynthetic algae. A similar mechanism could be active in seasonally stratified lakes and marine basins such as the Black Sea, where light penetrates to the anoxic chemocline. Given the widespread occurrence of seasonally stratified anoxic lakes, aerobic methane oxidn. coupled to oxygenic photosynthesis might have an important but so far neglected role in methane emissions from lakes.
- 3Blees, J.; Niemann, H.; Wenk, C. B.; Zopfi, J.; Schubert, C. J.; Kirf, M. K.; Veronesi, M. L.; Hitz, C.; Lehmann, M. F. Micro-aerobic bacterial methane oxidation in the chemocline and anoxic water column of deep south-Alpine Lake Lugano (Switzerland). Limnol. Oceanogr. 2014, 59 (2), 311– 324, DOI: 10.4319/lo.2014.59.2.03113https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXosVyitbc%253D&md5=70effabb765ba8ff51fb82d9f2063db4Micro-aerobic bacterial methane oxidation in the chemocline and anoxic water column of deep south-Alpine Lake Lugano (Switzerland)Blees, Jan; Niemann, Helge; Wenk, Christine B.; Zopfi, Jakob; Schubert, Carsten J.; Kirf, Mathias K.; Veronesi, Mauro L.; Hitz, Carmen; Lehmann, Moritz F.Limnology and Oceanography (2014), 59 (2), 311-324CODEN: LIOCAH; ISSN:0024-3590. (Association for the Sciences of Limnology and Oceanography, Inc.)We measured seasonal variations in the vertical distribution of methane concn., methane oxidn. rates, and lipid biomarkers in the northern basin of Lake Lugano. Methane consumption below the oxic-anoxic interface co-occurred with concn. maxima of 13C-depleted C16 fatty acid biomarkers (with δ13C values as low as -70‰) in the anoxic water column, as well as characteristic δ13CCH4 profiles. We argue that the conspicuous methane concn. gradients are primarily driven by (micro-)aerobic methane oxidn. (MOx) below the chemocline. We measured a strong MOx potential throughout the anoxic water column, while MOx rates at in situ O2 concn. > 10 nmol L-1 were undetectable. Similarly, we found MOx-related biomarkers and gene sequences encoding the particulate methane monooxygenase in the anoxic, but not the oxic, water. The mechanism of (episodic) oxygen supply sustaining the MOx community in anoxic waters is still uncertain. Our results indicate that a bacterial methanotrophic community is responsible for the methane consumption in Lake Lugano, without detectable contribution from archaeal methanotrophs. Bacterial populations that accumulated both at the suboxic-anoxic interface and in the deeper anoxic hypolimnion, where max. potential MOx rates were obsd. throughout the year (1.5-2.5 μmol L-1 d-1) were mainly related to Methylobacter sp. Close relatives are found in lacustrine environments throughout the world, and their potential to thrive under micro- and anoxic conditions in Lake Lugano may imply that micro-aerobic methane oxidn. is important in methane cycling and competition for methane and oxygen in stratified lakes worldwide.
- 4Wetzel, R. G. The inorganic carbon complex. In Limnology, 3rd ed.; Academic Press: San Diego, CA, 2001; pp 187– 204.There is no corresponding record for this reference.
- 5Stocker, R. Marine Microbes See a Sea of Gradients. Science 2012, 338 (6107), 628– 633, DOI: 10.1126/science.12089295https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhsFygtbvE&md5=5345311b56a07384ccbe0bbce591fb19Marine Microbes See a Sea of GradientsStocker, RomanScience (Washington, DC, United States) (2012), 338 (6107), 628-633CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)A review. Marine bacteria influence Earth's environmental dynamics in fundamental ways by controlling the biogeochem. and productivity of the oceans. These large-scale consequences result from the combined effect of countless interactions occurring at the level of the individual cells. At these small scales, the ocean is surprisingly heterogeneous, and microbes experience an environment of pervasive and dynamic chem. and phys. gradients. Many species actively exploit this heterogeneity, while others rely on gradient-independent adaptations. This is an exciting time to explore this frontier of oceanog., but understanding microbial behavior and competition in the context of the water column's microarchitecture calls for new ecol. frameworks, such as a microbial optimal foraging theory, to det. the relevant trade-offs and global consequences of microbial life in a sea of gradients.
- 6Byrne, R. H. Measuring Ocean Acidification: New Technology for a New Era of Ocean Chemistry. Environ. Sci. Technol. 2014, 48 (10), 5352– 5360, DOI: 10.1021/es405819p6https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXls1KqsbY%253D&md5=4f1df867ea47c033baecba1ba2f44023Measuring Ocean Acidification: New Technology for a New Era of Ocean ChemistryByrne, Robert H.Environmental Science & Technology (2014), 48 (10), 5352-5360CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)Human addns. of carbon dioxide to the atm. are creating a cascade of chem. consequences that will eventually extend to the bottom of all the world's oceans. Among the best-documented seawater effects are a worldwide increase in open-ocean acidity and large-scale declines in calcium carbonate satn. states. The susceptibility of some young, fast-growing calcareous organisms to adverse impacts highlights the potential for biol. and economic consequences. Many important aspects of seawater CO2 chem. can be only indirectly obsd. at present, and important but difficult-to-observe changes can include shifts in the speciation and possibly bioavailability of some life-essential elements. Innovation and invention are urgently needed to develop the in situ instrumentation required to document this era of rapid ocean evolution.
- 7Abril, G.; Bouillon, S.; Darchambeau, F.; Teodoru, C. R.; Marwick, T. R.; Tamooh, F.; Ochieng Omengo, F.; Geeraert, N.; Deirmendjian, L.; Polsenaere, P.; Borges, A. V. Technical Note: Large overestimation of pCO2 calculated from pH and alkalinity in acidic, organic-rich freshwaters. Biogeosciences 2015, 12 (1), 67– 78, DOI: 10.5194/bg-12-67-20157https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhsVantrfL&md5=4c83158f0b16066b94207f84aa02ad48Technical note: large overestimation of pCO2 calculated from pH and alkalinity in acidic, organic-rich freshwatersAbril, G.; Bouillon, S.; Darchambeau, F.; Teodoru, C. R.; Marwick, T. R.; Tamooh, F.; Omengo, F. Ochieng; Geeraert, N.; Deirmendjian, L.; Polsenaere, P.; Borges, A. V.Biogeosciences (2015), 12 (1), 67-78CODEN: BIOGGR; ISSN:1726-4189. (Copernicus Publications)Inland waters have been recognized as a significant source of carbon dioxide (CO2) to the atm. at the global scale. Fluxes of CO2 between aquatic systems and the atm. are calcd. from the gas transfer velocity and the water-air gradient of the partial pressure of CO2 (pCO2). Currently, direct measurements of water pCO2 remain scarce in freshwaters, and most published pCO2 data are calcd. from temp., pH and total alky. (TA). Here, we compare calcd. (pH and TA) and measured (equilibrator and headspace) water pCO2 in a large array of temperate and tropical freshwaters. The 761 data points cover a wide range of values for TA (0 to 14 200 μmol L-1), pH (3.94 to 9.17), measured pCO2 (36 to 23 000 ppmv), and dissolved org. carbon (DOC) (29 to 3970 μmol L-1). Calcd. pCO2 were >10% higher than measured pCO2 in 60% of the samples (with a median overestimation of calcd. pCO2 compared to measured pCO2 of 2560 ppmv) and were >100% higher in the 25% most org.-rich and acidic samples (with a median overestimation of 9080 ppmv). We suggest these large overestimations of calcd. pCO2 with respect to measured pCO2 are due to the combination of two cumulative effects: (1) a more significant contribution of org. acids anions to TA in waters with low carbonate alky. and high DOC concns.; (2) a lower buffering capacity of the carbonate system at low pH, which increases the sensitivity of calcd. pCO2 to TA in acidic and organicrich waters. No empirical relationship could be derived from our data set in order to correct calcd. pCO2 for this bias. Owing to the widespread distribution of acidic, org.-rich freshwaters, we conclude that regional and global ests. of CO2 outgassing from freshwaters based on pH and TA data only are most likely overestimated, although the magnitude of the overestimation needs further quant. anal. Direct measurements of pCO2 are recommended in inland waters in general, and in particular in acidic, poorly buffered freshwaters.
- 8Liu, X.; Byrne, R. H.; Adornato, L.; Yates, K. K.; Kaltenbacher, E.; Ding, X.; Yang, B. In Situ Spectrophotometric Measurement of Dissolved Inorganic Carbon in Seawater. Environ. Sci. Technol. 2013, 47 (19), 11106– 11114, DOI: 10.1021/es40148078https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhtlClsbbE&md5=39af5e62bcfe3ca7dc983f036fba43b7In Situ Spectrophotometric Measurement of Dissolved Inorganic Carbon in SeawaterLiu, Xuewu; Byrne, Robert H.; Adornato, Lori; Yates, Kimberly K.; Kaltenbacher, Eric; Ding, Xiaoling; Yang, BoEnvironmental Science & Technology (2013), 47 (19), 11106-11114CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)Autonomous in situ sensors are needed to document the effects of today's rapid ocean uptake of atm. CO2 (e.g., ocean acidification). General environmental conditions (e.g., biofouling, turbidity) and C-specific conditions (e.g., wide diel variations) present significant challenges to acquiring long-term measurements of dissolved inorg. C (DIC) with satisfactory accuracy and resoln. SEAS-DIC is a new in situ instrument designed to provide calibrated, high-frequency, long-term measurements of DIC in marine and fresh waters. Sample water is 1st acidified to convert all DIC to CO2. The sample and a known reagent soln. are then equilibrated across a gas-permeable membrane. Spectrophotometric measurement of reagent pH can thereby det. the sample DIC over a wide dynamic range, with inherent calibration provided by the pH indicator's mol. characteristics. Field trials indicate that SEAS-DIC performs well in biofouling and turbid waters, with a DIC accuracy and precision of ∼2 μmol/Kg and a measurement rate of ∼1/min. The acidic reagent protects the sensor cell from biofouling, and the gas-permeable membrane excludes particulates from the optical path. This instrument, the 1st spectrophotometric system capable of automated in situ DIC measurements, positions DIC to become a key parameter for in situ CO2-system characterizations.
- 9Wang, Z. A.; Sonnichsen, F. N.; Bradley, A. M.; Hoering, K. A.; Lanagan, T. M.; Chu, S. N.; Hammar, T. R.; Camilli, R. In Situ Sensor Technology for Simultaneous Spectrophotometric Measurements of Seawater Total Dissolved Inorganic Carbon and pH. Environ. Sci. Technol. 2015, 49 (7), 4441– 4449, DOI: 10.1021/es504893n9https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXjsVCqurs%253D&md5=2157ec02f0ec262d21bf8d1b70811226In Situ Sensor Technology for Simultaneous Spectrophotometric Measurements of Seawater Total Dissolved Inorganic Carbon and pHWang, Zhaohui Aleck; Sonnichsen, Frederick N.; Bradley, Albert M.; Hoering, Katherine A.; Lanagan, Thomas M.; Chu, Sophie N.; Hammar, Terence R.; Camilli, RichardEnvironmental Science & Technology (2015), 49 (7), 4441-4449CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)A new, in situ sensing system, Channelized Optical System (CHANOS), was recently developed to make high-resoln., simultaneous measurements of total dissolved inorg. carbon (DIC) and pH in seawater. Measurements made by this single, compact sensor can fully characterize the marine carbonate system. The system has a modular design to accommodate two independent, but similar measurement channels for DIC and pH. Both are based on spectrophotometric detection of hydrogen ion concns. The pH channel uses a flow-through, sample-indicator mixing design to achieve near instantaneous measurements. The DIC channel adapts a recently developed spectrophotometric method to achieve flow-through CO2 equilibration between an acidified sample and an indicator soln. with a response time of only ∼90 s. During lab. and in situ testing, CHANOS achieved a precision of ±0.0010 and ±2.5 μmol/kg for pH and DIC, resp. In situ comparison tests indicated that the accuracies of the pH and DIC channels over a three-week time-series deployment were ±0.0024 and ±4.1 μmol/kg, resp. This study demonstrates that CHANOS can make in situ, climatol.-quality measurements by measuring two desirable CO2 parameters, and is capable of resolving the CO2 system in dynamic marine environments.
- 10Martz, T. R.; Dickson, A. G.; DeGrandpre, M. D. Tracer Monitored Titrations: Measurement of Total Alkalinity. Anal. Chem. 2006, 78 (6), 1817– 1826, DOI: 10.1021/ac051613310https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28XhtlersL0%253D&md5=eb5c1c0e5602498887ab49ce33b0023fTracer Monitored Titrations: Measurement of Total AlkalinityMartz, Todd R.; Dickson, Andrew G.; DeGrandpre, Michael D.Analytical Chemistry (2006), 78 (6), 1817-1826CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)We introduce a new titrn. methodol., tracer monitored titrn. (TMT), in which analyses are free of volumetric and gravimetric measurements and insensitive to pump precision and reproducibility. Spectrophotometric monitoring of titrant diln., rather than vol. increment, lays the burden of anal. performance solely on the spectrophotometer. In the method described here, the titrant is a standardized mixt. of acid-base indicator and strong acid. Diln. of a pulse of titrant in a titrn. vessel is tracked using the total indicator concn. measured spectrophotometrically. The concns. of reacted and unreacted indicator species, derived from Beer's law, are used to calc. the relative proportions of titrant and sample in addn. to the equil. position (pH) of the titrn. mixt. Because the method does not require volumetric or gravimetric addns. of titrant, simple low-precision pumps can be used. Here, we demonstrate application of TMT for detn. of total alky. (AT). High-precision, high-accuracy seawater AT measurements are crucial for understanding, for example, the marine CaCO3 budget and satn. state, anthropogenic CO2 penetration into the oceans, calcareous phytoplankton blooms, and coral reef dynamics. We present data from 286 titrns. on three types of total alky. stds.: Na2CO3 in 0.7 mol/kg ·soln of NaCl, NaOH in 0.7 mol/kg soln NaCl, and a seawater Certified Ref. Material (CRM). Based on Na2CO3 stds., the accuracy and precision are ±0.2 and ±0.1% (4 and 2 μmol/kg soln for AT ∼2100-2500 μmol/kg soln, n = 242), using low-precision solenoid pumps to introduce sample and titrant. Similar accuracy and precision were found for analyses run 42 days after the initial expts. Excellent performance is achieved by optimizing the spectrophotometric detection system and relying upon basic chem. thermodn. for calcg. the equivalence point. Although applied to acid-base titrns. in this paper, the approach should be generally applicable to other types of titrns.
- 11Bell, R. J.; Short, R. T.; Byrne, R. H. In situ determination of total dissolved inorganic carbon by underwater membrane introduction mass spectrometry. Limnol. Oceanogr.: Methods 2011, 9 (4), 164– 175, DOI: 10.4319/lom.2011.9.16411https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXmt1Kms70%253D&md5=e041059b257b71d0857a9dcd3aa93711In situ determination of total dissolved inorganic carbon by underwater membrane introduction mass spectrometryBell, Ryan I.; Short, R. Timothy; Byrne, Robert H.Limnology and Oceanography: Methods (2011), 9 (April), 164-175CODEN: LOMIBY; ISSN:1541-5856. (American Society of Limnology and Oceanography)Procedures have been developed for the detn. of total dissolved inorg. C (DIC) in acidified seawater using an underwater mass spectrometer. Factors affecting the response of the membrane introduction mass spectrometer (MIMS) system were examd. to optimize calibrations and enhance the accuracy of component ocean C system measurements. Lab. studies examd. the following influences on MIMS measurements of DIC: bicarbonate and carbonate contributions to the MIMS CO2 signal intensity, linearity of MIMS response over a wide range of CO2 concns., influence of sample salinity on membrane permeability, and capability to use acidified solns. for calibrations of both DIC and CO2 fugacity. (a) bicarbonate and carbonate contributions to CO2 signal intensity were significant at slow flow rates, (b) MIMS response was linearly dependent on DIC within the concn. range of interest, (c) salinity has a discernable influence on membrane permeability i.e., in turn, dependent on hydrostatic pressure, and (d) well calibrated MIMS measurements for both DIC and CO2 fugacity can be obtained using acidified DIC stds. High flow rates are required during CO2 fugacity measurements in circumneutral seawater to eliminate signal contributions from bicarbonate and carbonate.
- 12Brennwald, M. S.; Schmidt, M.; Oser, J.; Kipfer, R. A Portable and Autonomous Mass Spectrometric System for On-Site Environmental Gas Analysis. Environ. Sci. Technol. 2016, 50 (24), 13455– 13463, DOI: 10.1021/acs.est.6b0366912https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhvFSit7fF&md5=d8b9b0f48c11b27b9d9babeb5ee17b16A Portable and Autonomous Mass Spectrometric System for On-Site Environmental Gas AnalysisBrennwald, Matthias S.; Schmidt, Mark; Oser, Julian; Kipfer, RolfEnvironmental Science & Technology (2016), 50 (24), 13455-13463CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)The authors developed a portable mass spectrometric system (miniRuedi) to quantify He and Ne (in dry gas), and Ar, Kr, N2, O2, CO2, and CH4 partial pressures in gaseous and aq. matrixes in environmental systems with an anal. uncertainty of 1-3%. The miniRuedi does not require purifn. or other prepn. of sampled gas; thus, it allows maintenance-free, autonomous operation. The app. is most suit able for on-site gas anal. during field work and at remote sites due to its small size (60 × 40 × 14 cm), low wt. (13 kg), and low power consumption (50 W). Gases are continuously sampled and transferred through a capillary pressure redn. system into a vacuum chamber where they are analyzed by quadrupole mass spectrometry with a 1-min resoln. time. The low gas consumption rate (<0.1 mL/min) minimizes interference with the gaseous natural mass balance in environmental systems, and allows unbiased quantification of dissolved gas concns. in water by gas/water equilibration using membrane contractors (gas equil./membrane inlet mass spectrometry, GE-MIMS). MiniRuedi performance was demonstrated in lab. and field tests and its utility was illustrated in field applications related to soil gas formation, lake/atm. gas exchange, and seafloor gas emanations.
- 13Kirf, M. K.; Dinkel, C.; Schubert, C. J.; Wehrli, B. Submicromolar Oxygen Profiles at the Oxic–Anoxic Boundary of Temperate Lakes. Aquat. Geochem. 2014, 20 (1), 39– 57, DOI: 10.1007/s10498-013-9206-713https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXitFChtrk%253D&md5=14bfa750a539f241713953a4641648c4Submicromolar Oxygen Profiles at the Oxic-Anoxic Boundary of Temperate LakesKirf, Mathias K.; Dinkel, Christian; Schubert, Carsten J.; Wehrli, BernhardAquatic Geochemistry (2014), 20 (1), 39-57CODEN: AQGEFP; ISSN:1380-6165. (Springer)Elements involved in biogeochem. cycles undergo rapid turnover at the oxic-anoxic interface of stratified lakes. Here, the presence or absence of oxygen governs abiotic and biotic processes and rates. However, achieving a detailed sampling resoln. to precisely locate the oxic-anoxic interface is difficult due to a lack of fast, drift-free sensors in the working range of 10 to a few 1,000 nmol O2 L-1. Here, we demonstrate that conventional amperometric and optical microsensors can be used to resolve submicromolar oxygen concns. in a continuous profiling mode. The amperometric drift was drastically reduced by anoxic preconditioning. In situ offset correction in the anoxic layer and a high amplification scheme allowed for an excellent detection limit of < 10 nmol L-1. The optical microsensors also showed a similar performance with a detection limit of < 20 nmol L-1. Their drift stability allowed for a lab. calibration in combination with a minor in situ anoxic offset correction. The two different sensor systems showed virtually identical profiles during parallel use in stratified lakes. Both sensors were able to resolve the fine-scale structure at the oxic-anoxic interface and revealed hitherto unnoticed extended zones of submicromolar oxygen concns. even below a steep oxycline. The zones extended up to several meters and showed substantial vertical variability. These results underline the need of a precise localization of the oxic-anoxic interface on a submicromolar scale in order to constrain the relevant aerobic and anaerobic redox processes.
- 14Athavale, R.; Kokorite, I.; Dinkel, C.; Bakker, E.; Wehrli, B.; Crespo, G. A.; Brand, A. In Situ Ammonium Profiling Using Solid-Contact Ion-Selective Electrodes in Eutrophic Lakes. Anal. Chem. 2015, 87 (24), 11990– 11997, DOI: 10.1021/acs.analchem.5b0242414https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhvVGhs7vJ&md5=f45a56ee9162b8e04bddf8fd2018baa4In Situ Ammonium Profiling Using Solid-Contact Ion-Selective Electrodes in Eutrophic LakesAthavale, Rohini; Kokorite, Ilga; Dinkel, Christian; Bakker, Eric; Wehrli, Bernhard; Crespo, Gaston A.; Brand, AndreasAnalytical Chemistry (Washington, DC, United States) (2015), 87 (24), 11990-11997CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)A promising profiling setup for in situ measurements in lakes with potentiometric solid-contact ion-selective electrodes (SC-ISEs) and a data processing method for sensor calibration and drift correction are presented. The profiling setup consists of a logging system, which is equipped with a syringe sampler and sensors for the measurement of std. parameters including temp., cond., O and photosynthetically active radiation (PAR). The setup was expanded with SC-ISEs in galvanically sepd. amplifiers. The potential for high-resoln. profiling is studied by deploying the setup in the eutrophic Lake Rotsee (Lucerne, Switzerland), using 2 different designs of ammonium sensing SC-ISEs. Ammonium was chosen as a target analyte, since it is the most common reduced inorg. N species involved in various pathways of the N cycle and is therefore indicative of numerous biogeochem. processes that occur in lakes such as denitrification and primary prodn. One of the designs, which uses a composite C-nanotube-PVC-based membrane, suffered from sulfide poisoning in the deeper, sulfidic regions of the lake. In contrast, electrodes contg. a plasticizer-free methacrylate copolymer-based sensing layer on top of a conducting polymer layer as a transducer did not show this poisoning effect. The syringe samples drawn during continuous profiling were utilized to calibrate the electrode response. Reaction hotspots and steep gradients of ammonium concns. were identified on-site by monitoring the electrode potential online. Upon conversion to high-resoln. concn. profiles, fine scale features between the calibration points were displayed, which would have been missed by conventional limnol. sampling and subsequent lab. analyses. Thus, the presented setup with SC-ISEs tuned to analytes of interest can facilitate the study of biogeochem. processes that occur at the centimeter scale.
- 15Severinghaus, J. W.; Bradley, A. F. Electrodes for Blood pO2 and pCO2 Determination. J. Appl. Physiol. 1958, 13 (3), 515– 520, DOI: 10.1152/jappl.1958.13.3.51515https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaG1MXmtlWisw%253D%253D&md5=cfba9a07f1c725f87bbee35548b9872fElectrodes for blood pO2 and pCO2 determinationSeveringhaus, John W.; Bradley, A. FreemanJournal of Applied Physiology (1948-1976) (1958), 13 (), 515-20CODEN: JAPYAA; ISSN:0021-8987.Modifications are described in detail of the O electrode of Clark (Trans. Am. Soc. Artificial Internal Organs 2, 41(1956)) and of the CO2 electrode first described by Stow, et al. (C.A. 52, 3006f).
- 16Fietzek, P.; Kötzinger, A. Optimization of a Membrane-Based NDIR Sensor for Dissolved Carbon Dioxide. Proceedings of OceanObs’09: Sustained Ocean Observations and Information for Society, ESA, Publication WPP-306 2010, Venice, Italy, 21–25 September 2009; Hall, J., Harrison, D. E., Stammer, D., Eds.; European Space Agency, 2010.There is no corresponding record for this reference.
- 17Suzuki, H.; Arakawa, H.; Sasaki, S.; Karube, I. Micromachined Severinghaus-Type Carbon Dioxide Electrode. Anal. Chem. 1999, 71 (9), 1737– 1743, DOI: 10.1021/ac981146817https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1MXitVagtrc%253D&md5=5a378827b51c05d79424147bc0f8fa87Micromachined Severinghaus-Type Carbon Dioxide ElectrodeSuzuki, Hiroaki; Arakawa, Hiroaki; Sasaki, Satoshi; Karube, IsaoAnalytical Chemistry (1999), 71 (9), 1737-1743CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)The Severinghaus-type pCO2 electrode was miniaturized and batch-fabricated using semiconductor and micromachining techniques. Anodically grown iridium oxide film (AIROF) was employed as the pH sensing element to detect a local pH change caused by the infusion of CO2. The AIROF showed a super-Nernstian response with a slope of ∼-80 mV/pH at 25°. A novel thin-film Ag/AgCl structure was also used. It features a hydrophobic membrane which covers the entire silver layer and the AgCl layer grown from the periphery of the silver pattern. The open-circuit potential of the Ag/AgCl element drifted to the neg. side at -0.1 to -0.2 mV h-1. A microcavity in which the electrolyte soln. was filled was anisotropically etched in a silicon substrate, and a silicone rubber gas-permeable membrane was formed on the sensitive area. The miniature pCO2 electrode showed a distinct response to the variation in concn. of dissolved CO2. The inherent characteristics of the Severinghaus electrode were confirmed in terms of its response and calibration curve. The selectivity of the electrode was satisfactory in view of its application to clin. anal.
- 18Wang, Z. A.; Liu, X.; Byrne, R. H.; Wanninkhof, R.; Bernstein, R. E.; Kaltenbacher, E. A.; Patten, J. Simultaneous spectrophotometric flow-through measurements of pH, carbon dioxide fugacity, and total inorganic carbon in seawater. Anal. Chim. Acta 2007, 596 (1), 23– 36, DOI: 10.1016/j.aca.2007.05.04818https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXnsVKlu7w%253D&md5=4127e6cbdb0c854c23b3639633fef992Simultaneous spectrophotometric flow-through measurements of pH, carbon dioxide fugacity, and total inorganic carbon in seawaterWang, Zhaohui Aleck; Liu, Xuewu; Byrne, Robert H.; Wanninkhof, Rik; Bernstein, Renate E.; Kaltenbacher, Eric A.; Patten, JamesAnalytica Chimica Acta (2007), 596 (1), 23-36CODEN: ACACAM; ISSN:0003-2670. (Elsevier B.V.)An autonomous, multi-parameter, flow-through CO2 system was developed to simultaneously measure surface seawater pH, CO2 fugacity (fCO2), and total dissolved inorg. C (DIC). All 3 measurements are based on spectrophotometric detns. of soln. pH at multiple wavelengths using sulfonephthalein indicators. The pH optical cell was machined from a PEEK (polyetherether ketone) polymer rod bearing a bore-hole with an optical path-length of ∼15 cm. The fCO2 optical cell consists of Teflon AF 2400 (DuPont) capillary tubing sealed in a PEEK rod bore hole. This Teflon AF tubing is filled with a std. indicator soln. with fixed total alky., forming a liq. core wave-guide (LCW). The LCW functions as a long path-length (∼15 cm) optical cell and a membrane which equilibrates the internal std. soln. with external seawater. fCO2 is then detd. by measuring the pH of the internal soln. FCO2 is detd. by measuring the internal soln. pH. DIC is measured by detg. std. internal solns. pH in equil. with seawater which was acidified to convert all forms of DIC to CO2. The system runs repetitive measurement cycles with a sampling frequency of ∼7 samples (21 measurements)/h. It was used to measure surface seawater pH, fCO2, and DIC during the CLIVAR/CO2 A16S cruise in the South Atlantic Ocean, 2005. Field precisions were 0.0008 units for pH, 0.9 μatm for fCO2, and 2.4 μmol/kg for DIC. These field precisions are close to those obtained in the lab. Direct comparison of measurements and measurements obtained using established std. methods showed the system achieved field agreements of 0.0012 ± 0.0042 units for pH, 1.0 ± 2.5 μatm for fCO2, and 2.2 ± 6.0 μmol/kg for DIC. This system integrates spectrophotometric measurements of multiple CO2 parameters into a single package suitable for observations of seawater and freshwater.
- 19Morf, W. E.; Mostert, I. A.; Simon, W. Time response of potentiometric gas sensors to primary and interfering species. Anal. Chem. 1985, 57 (6), 1122– 1126, DOI: 10.1021/ac00283a03619https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL2MXhsF2mtLw%253D&md5=0d55c343fc1f5b3c4fcb06a38a652fc2Time response of potentiometric gas sensors to primary and interfering speciesMorf, Werner E.; Mostert, Irmgard A.; Simon, WilhelmAnalytical Chemistry (1985), 57 (6), 1122-6CODEN: ANCHAM; ISSN:0003-2700.A theor. anal. of the emf. response of gas sensors to interfering gases is presented. The treatment considers the example of CO2 electrodes and analyzes the time and concn. dependence of the interference by acids (HY). The selectivity exhibited by such gas sensors after short measuring periods or at low sample concns. is detd. by the ratio of the permeabilities of the gas-permeable membrane (PHY/PCO2), whereas the final equil. selectivity is given by the ratio of the acidity consts. of the species involved (KHY/KCO2). The predicted time- and concn.-dependent changes in selectivity are in agreement with exptl. findings for different sensor systems. The dynamic response to the primary species CO2 is also treated. The theor. expression derived permits a perfect fit of exptl. time-response curves.
- 20Lopez, M. E. Selectivity of the potentiometric carbon dioxide gas-sensing electrode. Anal. Chem. 1984, 56 (13), 2360– 2366, DOI: 10.1021/ac00277a02320https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL2cXlvVaks78%253D&md5=995da5eb2fd54802538e788fd23d5b82Selectivity of the potentiometric carbon dioxide gas-sensing electrodeLopez, M. E.Analytical Chemistry (1984), 56 (13), 2360-6CODEN: ANCHAM; ISSN:0003-2700.Exptl. and theor. investigations of the potentiometric pCO2 electrode were employed to establish a steady-state model for both org. and inorg. interferences at this electrode. The electrode response is governed primarily by the acidity rather than the volatility of the interferents. With the proposed model, quant. selectivity coeff. values could be calcd. in good agreement with exptl. detd. values.
- 21Athavale, R.; Dinkel, C.; Wehrli, B.; Bakker, E.; Crespo, G. A.; Brand, A. Robust Solid-Contact Ion Selective Electrodes for High-Resolution In Situ Measurements in Fresh Water Systems. Environ. Sci. Technol. Lett. 2017, 4 (7), 286– 291, DOI: 10.1021/acs.estlett.7b0013021https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXnsVWrtrY%253D&md5=a34360ca85238b58dfa03196a110ed01Robust Solid-Contact Ion Selective Electrodes for High-Resolution In Situ Measurements in Fresh Water SystemsAthavale, Rohini; Dinkel, Christian; Wehrli, Bernhard; Bakker, Eric; Crespo, Gaston A.; Brand, AndreasEnvironmental Science & Technology Letters (2017), 4 (7), 286-291CODEN: ESTLCU; ISSN:2328-8930. (American Chemical Society)Biogeochem. processes are often confined to very narrow zones in aquatic systems. Therefore, highly resolved in situ measurements are required to study these processes. Potentiometric solid-contact ion selective electrodes (SC-ISEs) are promising tools for such measurements. SC-ISEs show good performance in analyses under controlled exptl. conditions. Very few sensor designs, however, can sustain the challenges of natural water matrixes and external environmental conditions during in situ applications. We fabricated ammonium and pH selective SC-ISEs with functionalized multiwalled carbon nanotubes (f-MWCNT) as a solid contact. Their functionality was tested in the lab. and applied in situ for vertical profiling in a eutrophic lake. Sensors were insensitive to strong redox changes, high sulfide concns., and bright daylight conditions during the application in the lake. In addn., sensors are easily fabricated and exhibit short response times (<10 s). The proposed design of SC-ISEs based on f-MWCNTs is quite suitable for high-resoln. in situ profiling of ionic species in fresh water lakes.
- 22Xie, X.; Bakker, E. Non-Severinghaus potentiometric dissolved CO2 sensor with improved characteristics. Anal. Chem. 2013, 85 (3), 1332– 6, DOI: 10.1021/ac303534v22https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXlt1aqsQ%253D%253D&md5=01984610c75d7e5fe0add123d1a43088Non-Severinghaus Potentiometric Dissolved CO2 Sensor with Improved CharacteristicsXie, Xiaojiang; Bakker, EricAnalytical Chemistry (Washington, DC, United States) (2013), 85 (3), 1332-1336CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)A new type of carbon dioxide sensor comprising a pH glass electrode measured against a carbonate-selective membrane electrode based on a tweezer type carbonate ionophore is presented here for the 1st time. No cumbersome liq. junction based ref. element is used in this measurement. The sensor shows an expected Nernstian divalent response slope to dissolved CO2 over a wide range covering the routine environmental and physiol. PCO2 levels. Unlike the conventional Severinghaus CO2 probe for which the response is substantially delayed to up to 10 min due to diffusion of carbon dioxide into the internal compartment, the ion-selective CO2 sensor proposed here shows a response time (t95%) of 5 s. When used together with a traditional ref. electrode, the sensor system is confirmed to also monitor sample pH and carbonate along with carbon dioxide. A selectivity anal. suggests that Cl- does not interfere even at high concns., allowing one to explore this type of sensor probe for use in seawater or undiluted blood samples. The CO2 probe was used in an aquarium to monitor the CO2 levels caused by the diurnal cycles caused by the metab. of the aquatic plants and shows stable and reproducible results.
- 23Choi, Y. S.; Lvova, L.; Shin, J. H.; Oh, S. H.; Lee, C. S.; Kim, B. H.; Cha, G. S.; Nam, H. Determination of Oceanic Carbon Dioxide Using a Carbonate-Selective Electrode. Anal. Chem. 2002, 74 (10), 2435– 2440, DOI: 10.1021/ac010845923https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38XivVOis7o%253D&md5=43356d16091688b8bbf6eed043a7c8d6Determination of Oceanic Carbon Dioxide Using a Carbonate-Selective ElectrodeChoi, Yong Suk; Lvova, Larisa; Shin, Jae Ho; Oh, Seong Hee; Lee, Chang Suk; Kim, Byeong Hyo; Cha, Geun Sig; Nam, HakhyunAnalytical Chemistry (2002), 74 (10), 2435-2440CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)Potentiometric properties of PVC membrane-based electrodes prepd. with mol. tweezer-type neutral carriers, 3,12-bis(TFAB)CA and deoxy-3,12-bis(TFAB)CA, and trifluoroacetyl-p-decylbenzene (TFADB) were measured in buffered electrolytes (0.1 M Tris-H2SO4, pH 8.6 and 8.0) and artificial seawater. It was obsd. that deoxy-3,12-bis(TFAB)CA-based electrode provided greatly enhanced CO32- selectivity over Cl- (log KCO32-,Cl-POT ∼-6) and other minor anions present in seawater. Thus, the possibility of applying this carbonate-selective electrode for direct detn. of oceanic CO2 was assessed. Total CO2 (TCO2) concn. in Yellow Sea surface water was detd. with the deoxy-3,12-bis(TFAB)CA-based electrode, Severinghaus-type CO2 gas sensor, and traditional potentiometric titrn. methods. Results showed the carbonate-selective electrode provided accurate oceanic TCO2 detn. comparable to that obtained with the other methods. The anal. procedure based on a carbonate-selective electrode is clearly advantageous over conventional methods; it does not require sample pretreatment or extra reagents other than the std. calibration solns., while providing measured results directly and immediately.
- 24Lee, H. J.; Yoon, I. J.; Yoo, C. L.; Pyun, H.-J.; Cha, G. S.; Nam, H. Potentiometric Evaluation of Solvent Polymeric Carbonate-Selective Membranes Based on Molecular Tweezer-Type Neutral Carriers. Anal. Chem. 2000, 72 (19), 4694– 4699, DOI: 10.1021/ac991212l24https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3cXlslOrs7s%253D&md5=10e1d66389bf30b9e692a9ab40e9d954Potentiometric Evaluation of Solvent Polymeric Carbonate-Selective Membranes Based on Molecular Tweezer-Type Neutral CarriersLee, Han Jin; Yoon, In Joon; Yoo, Choong Leol; Pyun, Hyung-Jung; Cha, Geun Sig; Nam, HakhyunAnalytical Chemistry (2000), 72 (19), 4694-4699CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)Potentiometric properties of the ion-selective electrodes based on highly plasticized PVC membranes doped with the carbonate-selective cholic acid (CA) derivs. have been measured. The carbonate-selective neutral carriers have been prepd. by coupling one to three trifluoroacetobenzoyl (TFAB) groups to a cholic acid deriv. which has three hydroxyl linkers lining on the C3, C7, and C12 positions of its rigid steroidal ring structure. The membranes based on cholic acid derivs. with two TFABs [3,7-bis(TFAB)CA, 3,12-bis(TFAB)CA, and 7,12-bis(TFAB)CA] exhibited remarkably improved carbonate selectivity, indicating that the bis(TFAB)CAs behave like mol. tweezers for the carbonate ion. For example, 3,12-bis(TFAB)CA resulted in 10-300-fold-enhanced carbonate selectivity over other anions (e.g., salicylate, ClO4-, SCN-, HPO42-, NO3-, NO2-, Br-, and Cl-) compared to that of the neutral carriers with a single TFAB group. The distances between the carbonate binding centers of bis(TFAB)CAs, i.e., the carbonyl carbons of the two TFAB groups, are in the 7.3-7.9-Å range at the AM1 level semiempirical calcn., which is too far for the carbonate ion to form direct covalent bonding. The fast atom bombardment mass spectra of bis(TFAB)CAs show that significant fractions of the compds. are either mono- or dihydrated before complexing the carbonate ion. These findings seem to suggest that bis(TFAB)CAs recognize the incoming carbonate ion by forming both covalent and hydrogen bonding between the hydrated and unhydrated TFAB groups. The anal. utility of the carbonate-selective electrode based on 3,12-bis(TFAB)CA has been demonstrated by measuring the total carbon dioxide in human serum in the presence of lipophilic anion interferents, e.g., salicylate.
- 25de Beer, D.; Bissett, A.; de Wit, R.; Jonkers, H.; Köhler-Rink, S.; Nam, H.; Kim, B. H.; Eickert, G.; Grinstain, M. A microsensor for carbonate ions suitable for microprofiling in freshwater and saline environments. Limnol. Oceanogr.: Methods 2008, 6 (10), 532– 541, DOI: 10.4319/lom.2008.6.53225https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXhtVWqs77P&md5=8074d39543be457386550b77716ca2ccA microsensor for carbonate ions suitable for microprofiling in freshwater and saline environmentsde Beer, Dirk; Bissett, Andrew; de Wit, Rutger; Jonkers, Henk; Koehler-Rink, Stefanie; Nam, Hakyun; Kim, Byeong Hyo; Eickert, Gabriele; Grinstain, MorLimnology and Oceanography: Methods (2008), 6 (Oct.), 532-541CODEN: LOMIBY; ISSN:1541-5856. (American Society of Limnology and Oceanography)A novel carbonate microsensor, based on the ion-selective ionophore N,N,-dioctyl-3α, 12 α-bis(4-trifluoroacetylbenzoxy)-5β-cholan-24-amide, is presented. The sensor chem. and filling electrolyte, used previously for macrosensors, was improved for use in microsensors, and a simple calibration procedure was designed. The sensor is highly selective for carbonate, having a similar selectivity as the macrosensor, and is so insensitive to Cl- interference that it can be used in seawater. The ability to measure accurate profiles with the carbonate sensor was verified in agar gels with artificial carbonate gradients. Several environmental applications are presented, including photosynthesis and calcification measurements in freshwater stromatolites (tufas) and foraminifera. Carbonate profiles in illuminated and darkened hypersaline microbial mats were qual. as expected and aligned with the oxygen and pH profiles. The dissolved inorg. carbon profiles calcd. from local pH and carbonate values, however, did not follow the expected trends, both in the foraminifera and the hypersaline mat. Temporal and spatial heterogeneities make perfect alignment of pH and carbonate profiles, needed for DIC calcns., unrealistic. The calcn. of dissolved inorg. carbon microprofiles from pH and carbonate microprofiles is not recommended. The microsensor is highly useful in studies on calcification and decalcification, where direct concns. of carbonate and calcium ions are needed.
- 26Pankratova, N.; Crespo, G. A.; Afshar, M. G.; Crespi, M. C.; Jeanneret, S.; Cherubini, T.; Tercier-Waeber, M.-L.; Pomati, F.; Bakker, E. Potentiometric sensing array for monitoring aquatic systems. Environ. Sci.: Processes Impacts 2015, 17 (5), 906– 914, DOI: 10.1039/C5EM00038F26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXlt1ant7o%253D&md5=f93820ee32f7fdf68f4dd790540b51d4Potentiometric sensing array for monitoring aquatic systemsPankratova, Nadezda; Crespo, Gaston A.; Afshar, Majid Ghahraman; Crespi, Miquel Coll; Jeanneret, Stephane; Cherubini, Thomas; Tercier-Waeber, Mary-Lou; Pomati, Francesco; Bakker, EricEnvironmental Science: Processes & Impacts (2015), 17 (5), 906-914CODEN: ESPICZ; ISSN:2050-7895. (Royal Society of Chemistry)Since aquatic environments are highly heterogeneous and dynamic, there is the need in aquatic ecosystem monitoring to replace traditional approaches based on periodical sampling followed by lab. anal. with new automated techniques that allow one to obtain monitoring data with high spatial and temporal resoln. We report here on a potentiometric sensing array based on polymeric membrane materials for the continuous monitoring of nutrients and chem. species relevant for the carbon cycle in freshwater ecosystems. The proposed setup operates autonomously, with measurement, calibration, fluidic control and acquisition triggers all integrated into a self-contained instrument. Exptl. validation was performed on an automated monitoring platform on lake Greifensee (Switzerland) using potentiometric sensors selective for hydrogen ions, carbonate, calcium, nitrate and ammonium. Results from the field tests were compared with those obtained by traditional lab. anal. A linear correlation between calcium and nitrate activities measured with ISEs and relevant concns. measured in the lab. was found, with the slopes corresponding to apparent single ion activity coeffs. [Formula Omitted] and [Formula Omitted]. Good correlation between pH values measured with ISE and CTD probes (SD = 0.2 pH) suggests adequate reliability of the methodol.
- 27Yuan, D.; Anthis, A. H. C.; Ghahraman Afshar, M.; Pankratova, N.; Cuartero, M.; Crespo, G. A.; Bakker, E. All-Solid-State Potentiometric Sensors with a Multiwalled Carbon Nanotube Inner Transducing Layer for Anion Detection in Environmental Samples. Anal. Chem. 2015, 87 (17), 8640– 8645, DOI: 10.1021/acs.analchem.5b0194127https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtlemurjO&md5=e0484a7b9d636d491402bcfb9953cd7cAll-Solid-State Potentiometric Sensors with a Multiwalled Carbon Nanotube Inner Transducing Layer for Anion Detection in Environmental SamplesYuan, Dajing; Anthis, Alexandre H. C.; Ghahraman Afshar, Majid; Pankratova, Nadezda; Cuartero, Maria; Crespo, Gaston A.; Bakker, EricAnalytical Chemistry (Washington, DC, United States) (2015), 87 (17), 8640-8645CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)While ion to electron transducing layers for the fabrication of potentiometric membrane electrodes for the detection of cations were well established, similar progress for the sensing of anions has not yet been realized. The authors report for this reason on a novel approach for the development of all-solid-state anion selective electrodes using lipophilic multiwalled carbon nanotubes (f-MWCNTs) as the inner ion to electron transducing layer. This material can be solvent cast, as it conveniently dissolves in THF, an important advantage to develop uniform films without the need for using surfactants that might deteriorate the performance of the electrode. Solid contact sensors for carbonate, nitrate, nitrite, and dihydrogen phosphate are fabricated and characterized, and all exhibit comparable anal. characteristics to the inner liq. electrodes. For example, the carbonate sensor exhibits a Nernstian slope of 27.2 ± 0.8 mV dec-1, a LOD = 2.3 μM, a response time of 1 s, a linear range of four logarithmic units, and a medium-term stability of 0.04 mV h-1 was obtained in a pH 8.6 buffered soln. Water layer test, reversibility, and selectivity for chloride, nitrate, and hydroxide are also reported. The excellent properties of f-MWCNTs as a transducer are contrasted to the deficient performance of poly(3-octyl-thiophene) (POT) for carbonate detection. This is evidenced both with a significant drift in the potentiometric measures as well as a pronounced sensitivity to light (either sunlight or artificial light). This latter aspect may compromise its potential for environmental in situ measurements (night/day cycles). The concn. of carbonate is detd. in a river sample (Arve river, Geneva) and compared to a ref. method (automatic titrator with potentiometric pH detection). Probably nanostructured materials such as f-MWCNTs are an attractive platform as a general ion-to-electron transducer for anion-selective electrodes.
- 28Brand, A.; Bruderer, H.; Oswald, K.; Guggenheim, C.; Schubert, C. J.; Wehrli, B. Oxygenic primary production below the oxycline and its importance for redox dynamics. Aquat. Sci. 2016, 78 (4), 727– 741, DOI: 10.1007/s00027-016-0465-428https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XitVOntrc%253D&md5=523289ceef04015d613a2cb46964de51Oxygenic primary production below the oxycline and its importance for redox dynamicsBrand, Andreas; Bruderer, Hannah; Oswald, Kirsten; Guggenheim, Carole; Schubert, Carsten J.; Wehrli, BernhardAquatic Sciences (2016), 78 (4), 727-741CODEN: AQSCEA; ISSN:1015-1621. (Birkhaeuser Basel)We present evidence that oxygenic primary prodn. occurs in the virtually anoxic regions (i.e. regions where no oxygen was detected) of the eutrophic, pre-alpine Lake Rot (Switzerland). Chlorophyll-a measurements in combination with phytoplankton densities indicated the presence of oxygenic primary producers throughout the water column. While Chlorophyceae were present as the main class of oxygenic phototrophs above the oxycline, which extended from 8 down to 9.2 m, the phototrophic community in and below the oxycline was dominated by cyanobacteria. In-situ incubation expts. with H14CO3- conducted in August 2013 revealed an oxygenic primary prodn. rate of 1.0 and 0.5 mg C m-3 h-1 in 9 and 10 m depth, resp. However, measurements with optical trace oxygen sensors showed that oxygen concns. were below the detection limit (20 nmol l-1) during the incubation period below 9.2 m. Potential oxygen consumption rates, which were 10-20 times higher than oxygen prodn. rates, explain this absence of free oxygen. Our data show that oxygen prodn. in the virtually anoxic zone corresponded to approx. 8 % of the oxygen flux driven by the concn. gradient in the oxycline. This provided an important source of electron acceptors for biogeochem. processes beyond the conventional redox boundary and in the apparently oxygen depleted zone of Lake Rot. This oxygenic primary prodn. in the virtually anoxic zone could allow growth and activity of aerobic microorganisms adapted to low oxygen supply.
- 29Müller, B.; Maerki, M.; Dinkel, C.; Stierli, R.; Wehrli, B. In Situ Measurements in Lake Sediments Using Ion-Selective Electrodes with a Profiling Lander System. In Environmental Electrochemistry; American Chemical Society, 2002; Vol. 811, pp 126– 143.There is no corresponding record for this reference.
- 30Cline, J. D. Spectrophotometric determination of hydrogen sulfide in natural waters. Limnol. Oceanogr. 1969, 14 (3), 454– 458, DOI: 10.4319/lo.1969.14.3.045430https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaF1MXksFegu70%253D&md5=d7e10415590a7dd4dc2e1c4c3896a0dbSpectrophotometric determination of hydrogen sulfide in natural watersCline, Joel D.Limnology and Oceanography (1969), 14 (3), 454-8CODEN: LIOCAH; ISSN:0024-3590.To det. dissolved H2S (H2S, HS-, S2-) in the concn. range of 1-1,000 μg./l., a mixed diamine reagent is used which is prepd. by dissolving 0.5-20 g. (depending on sulfide concn.) of N,N-dimethyl-p-phenylenediamine sulfate and FeCl3.6H2O (0.75-30.0 g. depending on sulfide concn.) in 500 ml. of cool 50% reagent grade HCl. In sulfide concn. in μmoles/l. is 1-3, the amt. of diamine is 0.5 g. and the Fe(III) is 0.75 g.; at 3-40, the diamine is 2.0 and Fe is 3.0; at 40-250 diamine is 8.0 and Fe is 12.0; at 250-1000 the diamine level is 20.0 and the Fe is 30.0. Exptl. a 50-ml. sample is transferred from the syringe to a 50-ml. serum bottle, to which 4 ml. of the appropriate mixed diamine reagent is added. A 5-ml. syringe with a 4-ml. stop position is satisfactory for reagent delivery. The serum cap is replaced promptly to reduce volatilization of the H2S and the soln. is mixed gently. After 20 min. the absorbance is detd. spectrophotometrically at 670 mμ in the appropriate cuvette. All necessary dilns. should be made after the color development time and in volumetric glassware. Diln. factors and path lengths are recommended for best results. Standardization is described and sensitivity, precision, and accuracy are detd. Temp. effect and interferences are discussed.
- 31Parkhurst, D. L. User’s Guide to PHREEQC: A Computer Program for Speciation, Reaction-Path, Advective-Transport, and Inverse Geochemical Calculations; U.S. Dept. of the Interior, U.S. Geological Survey: Denver, CO, 1995. https://search.library.wisc.edu/catalog/999778194102121.There is no corresponding record for this reference.
- 32Crespo, G. A.; Gugsa, D.; Macho, S.; Rius, F. X. Solid-contact pH-selective electrode using multi-walled carbon nanotubes. Anal. Bioanal. Chem. 2009, 395 (7), 2371– 2376, DOI: 10.1007/s00216-009-3127-832https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXhtFCnsrbN&md5=1640f851ca344ced4991fb8b25a47c3eSolid-contact pH-selective electrode using multi-walled carbon nanotubesCrespo, Gaston A.; Gugsa, Derese; Macho, Santiago; Rius, F. XavierAnalytical and Bioanalytical Chemistry (2009), 395 (7), 2371-2376CODEN: ABCNBP; ISSN:1618-2642. (Springer)Multi-walled C nanotubes (MWCNT) are efficient transducers of the ionic-to-electronic current. This enables the development of a new solid-contact pH-selective electrode that is based on the deposition of a 35-μm thick layer of MWCNT between the acrylic ion-selective membrane and the glassy C rod used as the elec. conductor. The ion-selective membrane was prepd. by incorporating tridodecylamine as the ionophore, K tetrakis[3,5-bis(trifluoromethyl)phenyl]borate as the lipophilic additive in a polymd. methylmethacrylate and an Bu acrylate matrix. The potentiometric response shows Nernstian behavior and a linear dynamic range between 2.89 and 9.90 pH values. The response time for this electrode was <10 s throughout the whole working range. The electrode shows a high selectivity towards interfering ions. Electrochem. impedance spectroscopy and chronopotentiometry techniques were used to characterize the electrochem. behavior and the stability of the C-nanotube-based ion-selective electrodes.
- 33Fibbioli, M.; Bandyopadhyay, K.; Liu, S.-G.; Echegoyen, L.; Enger, O.; Diederich, F.; Buhlmann, P.; Pretsch, E. Redox-active self-assembled monolayers as novel solid contacts for ion-selective electrodes. Chem. Commun. 2000, (5), 339– 340, DOI: 10.1039/a909532b33https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3cXhtlenu7o%253D&md5=df7b52db4206332b5fe02f40d357eb40Redox-active self-assembled monolayers as novel solid contacts for ion-selective electrodesFibbioli, Monia; Enger, Olivier; Diederich, Francois; Pretsch, Erno; Bandyopadhyay, Krisanu; Liu, Sheng-Gao; Echegoyen, Luis; Buhlmann, PhilippeChemical Communications (Cambridge) (2000), (5), 339-340CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)A new methodol. to fabricate solid-contact ion-selective electrodes (SC-ISEs) using SAMs of a lipophilic redox-active compd. to facilitate the charge transfer across the interface leads to improved potential stability and prevents redox or O2 interference of valinomycin-based SC-ISEs.
- 34Lindner, E.; Gyurcsanyi, R. E. Quality control criteria for solid-contact, solvent polymeric membrane ion-selective electrodes. J. Solid State Electrochem. 2009, 13 (1), 51– 68, DOI: 10.1007/s10008-008-0608-134https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXht1Knu7zI&md5=953a27fe92b19acc3301ad2f9493c3bfQuality control criteria for solid-contact, solvent polymeric membrane ion-selective electrodesLindner, Erno; Gyurcsanyi, Robert E.Journal of Solid State Electrochemistry (2009), 13 (1), 51-68CODEN: JSSEFS; ISSN:1432-8488. (Springer GmbH)A review. After a long history and conflicting views, solid-contact (SC) solvent polymeric membrane ion-selective electrodes (ISEs) emerged as reliable potentiometric-sensing devices with unique advantages. From the large variety of proposed SCs inherently conductive polymers emerged as the materials of choice. In the view, the most attractive feature of SC ISEs is their compatibility with thin- and thick-film micro-fabrication technologies that can provide cheap, mass-produced sensors and sensor arrays that can be integrated with the measuring, data acquisition, and control electronics in a straightforward way. However, despite the impressive properties of certain SC electrodes and their potential advantages, they remained primarily in the research labs. To make the jump from the research labs. into com. devices, it would be essential to prove that miniaturized SC ISEs can indeed match or surpass the performance characteristics of the conventional, liq.-contact macro-electrodes. It would be important to settle on the quality control criteria and testing protocols for assessing the performance characteristics of SC electrodes. It could help in interpreting the sometimes-inconsistent exptl. data. Once cheap, miniaturized, SC ISEs will match the performance characteristics of macroscopic-size electrodes, it is expected to have an important impact in a variety of applications requiring robust, maintenance-free, or single-use ISEs, e.g., in home care or bedside diagnostics, environmental anal., and quality control assessment. Reliable SC ISEs are expected to revitalize the field of ion-selective field effect transistors and open new possibilities in combination with nanowire-based devices.
- 35Mousavi, Z.; Teter, A.; Lewenstam, A.; Maj-Zurawska, M.; Ivaska, A.; Bobacka, J. Comparison of Multi-walled Carbon Nanotubes and Poly(3-octylthiophene) as Ion-to-Electron Transducers in All-Solid-State Potassium Ion-Selective Electrodes. Electroanalysis 2011, 23 (6), 1352– 1358, DOI: 10.1002/elan.20100074735https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXmvFCnt7o%253D&md5=bfaa4343fbea256f7946ea8bbf9a134aComparison of multi-walled carbon nanotubes and poly(3-octylthiophene) as ion-to-electron transducers in all-solid-state potassium ion-selective electrodesMousavi, Zekra; Teter, Agnieszka; Lewenstam, Andrzej; Maj-Zurawska, Magdalena; Ivaska, Ari; Bobacka, JohanElectroanalysis (2011), 23 (6), 1352-1358CODEN: ELANEU; ISSN:1040-0397. (Wiley-VCH Verlag GmbH & Co. KGaA)Multi-walled carbon nanotubes (MWCNTs) were compared with poly(3-octylthiophene) (POT) as ion-to-electron transducer in all-solid-state potassium ion-selective electrodes with valinomycin-based ion-selective membranes. MWCNTs and POT were mixed with the other components of the potassium ion-selective membrane cocktail (valinomycin, KTpClPB, o-NPOE, PVC, THF) which was then applied on a glassy carbon (GC) substrate to prep. single-piece ion-selective electrodes (SPISEs). Results from potentiometric and impedance measurements showed that the MWCNT-based electrodes have a more reproducible std. potential and a lower overall impedance than the electrodes based on POT. Both types of electrodes showed similar sensitivity to K+ and no redox sensitivity.
- 36Lindner, E.; Toth, K.; Pungor, E. Definition and determination of response time of ion selective electrodes. Pure Appl. Chem. 1986, 58 (3), 469– 479, DOI: 10.1351/pac19865803046936https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL28XitlKhtL4%253D&md5=15ceb89406c61c46f83646796d71de7cDefinition and determination of response time of ion selective electrodesLindner, E.; Toth, Klara; Pungor, E.Pure and Applied Chemistry (1986), 58 (3), 469-79CODEN: PACHAS; ISSN:0033-4545.A review with 30 refs. The topics include: concept of response time, detn. of response time, limits of the activity step method, definition of response time, and comparison of response time data calcd. according to different math. models and response time definitions.
- 37Oswald, K.; Milucka, J.; Brand, A.; Littmann, S.; Wehrli, B.; Kuypers, M. M. M.; Schubert, C. J. Light-Dependent Aerobic Methane Oxidation Reduces Methane Emissions from Seasonally Stratified Lakes. PLoS One 2015, 10 (7), e0132574 DOI: 10.1371/journal.pone.013257437https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhsV2rt7fI&md5=f49d5a6c069f047e0f33eaa5aee5b0acLight-dependent aerobic methane oxidation reduces methane emissions from seasonally stratified lakesOswald, Kirsten; Milucka, Jana; Brand, Andreas; Littmann, Sten; Wehrli, Bernhard; Kuypers, Marcel M. M.; Schubert, Carsten J.PLoS One (2015), 10 (7), e0132574/1-e0132574/22CODEN: POLNCL; ISSN:1932-6203. (Public Library of Science)Lakes are a natural source of methane to the atm. and contribute significantly to total emissions compared to the oceans. Controls on methane emissions from lake surfaces, particularly biotic processes within anoxic hypolimnia, are only partially understood. Here we investigated biol. methane oxidn. in the water column of the seasonally stratified Lake Rotsee. A zone of methane oxidn. extending from the oxic/anoxic interface into anoxic waters was identified by chem. profiling of oxygen, methane and δ13C of methane. Incubation expts. with 13C-methane yielded highest oxidn. rates within the oxycline, and comparable rates were measured in anoxic waters. Despite predominantly anoxic conditions within the zone of methane oxidn., known groups of anaerobic methanotrophic archaea were conspicuously absent. Instead, aerobic gammaproteobacterial methanotrophs were identified as the active methane oxidizers. In addn., continuous oxidn. and max. rates always occurred under light conditions. These findings, along with the detection of chlorophyll a, suggest that aerobic methane oxidn. is tightly coupled to light-dependent photosynthetic oxygen prodn. both at the oxycline and in the anoxic bottom layer. It is likely that this interaction between oxygenic phototrophs and aerobic methanotrophs represents a widespread mechanism by which methane is oxidized in lake water, thus diminishing its release into the atm.
Supporting Information
Supporting Information
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.est.8b02969.
Experimental section with materials and chemicals, sensor fabrication, laboratory tests, sulfide sensitivity test (Figure S1), schemes in optimization of in situ calibration protocol (Figure S2), depth profile of raw and drift corrected ΔEMF (Figure S3), depth profiles of activity of dissolved CO2 obtained by CO2–SH probe with different calibration schemes (Figure S4), in situ profiling set up (Figure S5), selectivity coefficients for ion selective membranes and mean concentrations of relevant ions in the lake water column (Table S1), and performance of SC-ISEs during laboratory tests (Table S2) (PDF)
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