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Nagy X, Höfler L. Lowering Detection Limits Toward Target Ions Using Quasi-Symmetric Polymeric Ion-Selective Membranes Combined with Amperometric Measurements. Anal Chem 2016; 88:9850-9855. [DOI: 10.1021/acs.analchem.6b03043] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Xénia Nagy
- Department of Inorganic
and
Analytical Chemistry, Budapest University of Technology and Economics, Szt. Gellért tér 4, Budapest, 1111, Hungary
| | - Lajos Höfler
- Department of Inorganic
and
Analytical Chemistry, Budapest University of Technology and Economics, Szt. Gellért tér 4, Budapest, 1111, Hungary
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2
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Jarolímová Z, Crespo GA, Xie X, Ghahraman Afshar M, Pawlak M, Bakker E. Chronopotentiometric Carbonate Detection with All-Solid-State Ionophore-Based Electrodes. Anal Chem 2014; 86:6307-14. [DOI: 10.1021/ac5004163] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Zdeňka Jarolímová
- Department of Inorganic and
Analytical Chemistry, University of Geneva, Quai Ernest-Ansermet 30, CH-1211 Geneva, Switzerland
| | - Gastón A. Crespo
- Department of Inorganic and
Analytical Chemistry, University of Geneva, Quai Ernest-Ansermet 30, CH-1211 Geneva, Switzerland
| | - Xiaojiang Xie
- Department of Inorganic and
Analytical Chemistry, University of Geneva, Quai Ernest-Ansermet 30, CH-1211 Geneva, Switzerland
| | - Majid Ghahraman Afshar
- Department of Inorganic and
Analytical Chemistry, University of Geneva, Quai Ernest-Ansermet 30, CH-1211 Geneva, Switzerland
| | - Marcin Pawlak
- Department of Inorganic and
Analytical Chemistry, University of Geneva, Quai Ernest-Ansermet 30, CH-1211 Geneva, Switzerland
| | - Eric Bakker
- Department of Inorganic and
Analytical Chemistry, University of Geneva, Quai Ernest-Ansermet 30, CH-1211 Geneva, Switzerland
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Ghahraman Afshar M, Crespo GA, Bakker E. Direct Ion Speciation Analysis with Ion-Selective Membranes Operated in a Sequential Potentiometric/Time Resolved Chronopotentiometric Sensing Mode. Anal Chem 2012; 84:8813-21. [DOI: 10.1021/ac302092m] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Majid Ghahraman Afshar
- Department of Inorganic
and Analytical Chemistry, University of Geneva, Quai Ernest-Ansermet 30, CH-1211
Geneva, Switzerland
| | - Gastón A. Crespo
- Department of Inorganic
and Analytical Chemistry, University of Geneva, Quai Ernest-Ansermet 30, CH-1211
Geneva, Switzerland
| | - Eric Bakker
- Department of Inorganic
and Analytical Chemistry, University of Geneva, Quai Ernest-Ansermet 30, CH-1211
Geneva, Switzerland
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Abu Shawish HM, Saadeh SM, Al-Dalou AR, Ghalwa NA, Assi AAA. Optimization of tramadol–PVC membrane electrodes using miscellaneous plasticizers and ion-pair complexes. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2011. [DOI: 10.1016/j.msec.2010.09.014] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Grygolowicz-Pawlak E, Bakker E. Thin Layer Coulometry with Ionophore Based Ion-Selective Membranes. Anal Chem 2010; 82:4537-42. [DOI: 10.1021/ac100524z] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ewa Grygolowicz-Pawlak
- Department of Chemistry, Nanochemistry Research Institute, Curtin University of Technology, Perth, WA 6845, Australia
| | - Eric Bakker
- Department of Chemistry, Nanochemistry Research Institute, Curtin University of Technology, Perth, WA 6845, Australia
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Höfler L, Bedlechowicz I, Vigassy T, Gyurcsányi RE, Bakker E, Pretsch E. Limitations of current polarization for lowering the detection limit of potentiometric polymeric membrane sensors. Anal Chem 2009; 81:3592-9. [PMID: 19338286 DOI: 10.1021/ac802588j] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Ion fluxes across polymeric ion-selective membranes are a decisive parameter dictating the lower detection limit of potentiometric ion sensors. An applied current was earlier proposed to counteract such fluxes and reduce the detection limit to ultratrace levels. So far, however, the method has not been used in practical situations since the correct current amplitude requires prior knowledge of the sample composition. This paper explores the use of the stir effect to evaluate the optimal current by theory and experiments. It is shown that the traditionally used steady-state model assuming a uniform distribution of ion exchanger in the membrane, fixed with time, violates the electroneutrality condition. A modified steady-state model is introduced that allows for a concentration tilt of the ion exchanger and predicts that a stir effect can indeed be utilized to find the optimal current. Ideally, by choosing the optimal current and very long measurement times, the thermodynamic detection limit might be obtained. However, in practice the stir effect declines at low concentrations and the conditions are far from steady state. Therefore, the improvement of the lower detection limit achievable by galvanostatic control is only about 1 order of magnitude. A numerical finite-difference approximation is shown to trace the experimental potential responses of silver-selective electrodes well and to reproduce the stir effect adequately, even for different conditioning protocols. The stir effect is successfully used to improve the detection limit of electrodes with ill-optimized inner solutions; however, significant improvements beyond what is commonly feasible by chemical optimization does not seem to be easily achievable. The results indicate that with conventional membranes the possibility of improving the detection limit by current polarization is much more limited than assumed so far.
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Affiliation(s)
- Lajos Höfler
- Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, H-1111 Budapest, Hungary
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Bazylak G, Monge ME, Everaert J, Nagels LJ. Hydrophobicity-aided potentiometric detection of catecholamines, beta-agonists, and beta-blockers in a mixed-solvent capillary electrophoresis system. J Sep Sci 2009; 32:135-46. [DOI: 10.1002/jssc.200800450] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Xu Y, Ngeontae W, Pretsch E, Bakker E. Backside calibration chronopotentiometry: using current to perform ion measurements by zeroing the transmembrane ion flux. Anal Chem 2008; 80:7516-23. [PMID: 18778039 PMCID: PMC2597783 DOI: 10.1021/ac800774e] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A recent new direction in ion-selective electrode (ISE) research utilizes a stir effect to indicate the disappearance of an ion concentration gradient across a thin ion-selective membrane. This zeroing experiment allows one to evaluate the equilibrium relationship between front and backside solutions contacting the membrane by varying the backside solution composition. This method is attractive since the absolute potential during the measurement is not required, thus avoiding standard recalibrations from the sample solution and a careful control of the reference electrode potential. We report here on a new concept to alleviate the need to continuously vary the composition of the backside solution. Instead, transmembrane ion fluxes are counterbalanced at an imposed critical current. A theoretical model illustrates the relationship between the magnitude of this critical current and the concentration of analyte and countertransporting ions and is found to correspond well with experimental results. The approach is demonstrated with lead(II)-selective membranes and protons as dominating interference ions, and the concentration of Pb(2+) was successfully measured in tap water samples. The principle was further evaluated with calcium-selective membranes and magnesium as counterdiffusing species, with good results. Advantages and limitations arising from the kinetic nature of the perturbation technique are discussed.
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Affiliation(s)
- Yida Xu
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, USA
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Boswell PG, Anfang AC, Bühlmann P. Preparation of a Highly Fluorophilic Phosphonium Salt and its Use in a Fluorous Anion-Exchanger Membrane with High Selectivity for Perfluorinated Acids. J Fluor Chem 2008; 129:961-967. [PMID: 22072222 DOI: 10.1016/j.jfluchem.2008.05.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Fluorous solvents are the most nonpolar, nonpolarizable phases known, whereas ions are inherently polar. This makes it difficult to create salts that are soluble in a fluorous solvent. Here we present the synthesis and characterization of a new fluorophilic phosphonium salt, tris{3,5-bis[(perfluorooctyl)propyl]phenyl}methylphosphonium methyl sulfate. The salt has a solubility of at least 14 mM in perfluoro(perhydrophenanthrene), perfluoro(methylcyclohexane), and perfluorohexanes. It also shows immediate potential for use as a phase-transfer catalyst in fluorous biphasic catalysis, but in this work it is used as an anion exchanger site in the first potentiometric fluorous-membrane anion-selective electrode. The membrane sensor exhibited the exceptional selectivity of 3.9 × 10(10) to 1 for perfluorooctanesulfonate over chloride, and of 2.5 × 10(7) to 1 for perfluorooctanoate over chloride. With improvements to the sensor's detection limit and lifetime, it has the potential to be an attractive alternative to the expensive, time-consuming methods currently employed for measurement of perfluorinated acids.
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Affiliation(s)
- Paul G Boswell
- University of Minnesota, Department of Chemistry 207 Pleasant St. SE, Minneapolis, Minnesota 55455
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Affiliation(s)
- Benjamin J Privett
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
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Morf WE, Pretsch E, De Rooij NF. Theory and Computer Simulation of the Time-Dependent Selectivity Behavior of Polymeric Membrane Ion-Selective Electrodes. J Electroanal Chem (Lausanne) 2008; 614:15-23. [PMID: 20411043 DOI: 10.1016/j.jelechem.2007.10.027] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
A theoretical treatment of the time-dependent potential response of ion-selective electrodes to sample solutions containing primary and interfering ions is presented. The theory accounts for the influence of ion fluxes in the electrode membrane and the contacting aqueous sample layer and describes the variations in the apparent selectivity behavior as a function of the measuring time. The applicability of the theory is demonstrated by comparing predicted response curves with results of virtual experiments based on computer simulation. A close and convincing agreement was achieved for a large series of different examples, which confirms that the new theory can be successfully applied for general cases.
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Affiliation(s)
- W E Morf
- Institute of Microtechnology, University of Neuchâtel, Rue Jaquet-Droz 1, CH-2007 Neuchâtel, Switzerland
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Affiliation(s)
- Johan Bobacka
- Åbo Akademi University, Process Chemistry Centre, c/o Laboratory of Analytical Chemistry, Biskopsgatan 8, FI-20500 Turku-Åbo, Finland; Faculty of Material Science and Ceramics, AGH-University of Science and Technology, Al. Mickiewicza 30, PL-30059 Cracow, Poland; and Åbo Akademi University, Process Chemistry Centre, c/o Center for Process Analytical Chemistry and Sensor Technology (ProSens), Biskopsgatan 8, FI-20500 Turku-Åbo, Finland
| | - Ari Ivaska
- Åbo Akademi University, Process Chemistry Centre, c/o Laboratory of Analytical Chemistry, Biskopsgatan 8, FI-20500 Turku-Åbo, Finland; Faculty of Material Science and Ceramics, AGH-University of Science and Technology, Al. Mickiewicza 30, PL-30059 Cracow, Poland; and Åbo Akademi University, Process Chemistry Centre, c/o Center for Process Analytical Chemistry and Sensor Technology (ProSens), Biskopsgatan 8, FI-20500 Turku-Åbo, Finland
| | - Andrzej Lewenstam
- Åbo Akademi University, Process Chemistry Centre, c/o Laboratory of Analytical Chemistry, Biskopsgatan 8, FI-20500 Turku-Åbo, Finland; Faculty of Material Science and Ceramics, AGH-University of Science and Technology, Al. Mickiewicza 30, PL-30059 Cracow, Poland; and Åbo Akademi University, Process Chemistry Centre, c/o Center for Process Analytical Chemistry and Sensor Technology (ProSens), Biskopsgatan 8, FI-20500 Turku-Åbo, Finland
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Abstract
This paper gives an overview of the newest developments of polymeric membrane ion-selective electrodes. A short essence of the underlying theory is given, emphasizing how the electromotive force may be used to assess binding constants of the ionophore, and how the selectivity and detection limit are related to the underlying membrane processes. The recent developments in lowering the detection limits of ISEs are described, including recent approaches of developing all solid state ISEs, and breakthroughs in detecting ultra-small quantities of ions at low concentrations. These developments have paved the way to use potentiometric sensors as in ultra-sensitive affinity bioanalysis in conjunction with nanoparticle labels. Recent results establish that potentiometry compares favorably to electrochemical stripping analysis. Other new developments with ion-selective electrodes are also described, including the concept of backside calibration potentiometry, controlled current coulometry, pulsed chronopotentiometry, and localized flash titration with ion-selective membranes to design sensors for the direct detection of total acidity without net sample perturbation. These developments have further opened the field for exciting new possibilities and applications.
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Affiliation(s)
- Eric Bakker
- Nanochemistry Research Institute, Department of Applied Chemistry, Curtin University of Technology, Perth, WA 6845, Australia
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Bakker E, Bhakthavatsalam V, Gemene KL. Beyond potentiometry: robust electrochemical ion sensor concepts in view of remote chemical sensing. Talanta 2007; 75:629-35. [PMID: 18585124 DOI: 10.1016/j.talanta.2007.10.021] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2007] [Accepted: 10/11/2007] [Indexed: 11/25/2022]
Abstract
For about 100 years, potentiometry with ion-selective electrodes has been one of the dominating electroanalytical techniques. While great advances in terms of selective chemistries and materials have been achieved in recent years, the basic manner in which ion-selective membranes are used has not fundamentally changed. The potential readings are directly co-dependent on the potential at the reference electrode, which requires maintenance and for which very few accepted alternatives have been proposed. Fouling or clogging of the exposed electrode surfaces will lead to changes in the observed potential. At the same time, the Nernst equation predicts quite small potential changes, on the order of millivolts for concentration changes on the order of a factor two, making frequent recalibration, accurate temperature control and electrode maintenance key requirements of routine analytical measurements. While the relatively advanced selective materials developed for ion-selective sensors would be highly attractive for low power remote sensing application, one should consider solutions beyond classical potentiometry to make this technology practically feasible. This paper evaluates some recent examples that may be attractive solutions to the stated problems that face potentiometric measurements. These include high-amplitude sensing approaches, with sensitivities that are an order of magnitude larger than predicted by the Nernst equation; backside calibration potentiometry, where knowledge of the magnitude of the potential is irrelevant and the system is evaluated from the backside of the membrane; controlled current coulometry with ion-selective membranes, an attractive technique for calibration-free reagent delivery without the need for standards or volumetry; localized electrochemical titrations at ion-selective membranes, making it possible to design sensors that directly monitor parameters such as total acidity for which volumetric techniques were traditionally used; and controlled potential coulometry, where all ions of interest are selectively transferred into the ion-selective organic phase, forming a calibration-free technique that would be exquisitely suitable for remote sensing applications.
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Affiliation(s)
- Eric Bakker
- Department of Chemistry, 560 Oval Drive, Purdue University, West Lafayette, IN 47907, USA
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Ngeontae W, Xu Y, Xu C, Aeungmaitrepirom W, Tuntulani T, Pretsch E, Bakker E. Sensitivity and working range of backside calibration potentiometry. Anal Chem 2007; 79:8705-11. [PMID: 17929899 DOI: 10.1021/ac071248a] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A new direction in potentiometric sensing, termed backside calibration potentiometry, was recently introduced. It makes use of the fact that the stir effect disappears in the absence of an ion-ionophore complex concentration gradient across supported liquid ion-selective membranes. This method is especially suitable for measurements in which recalibration in the sample is not feasible, such as in remote monitoring applications. Here, a theoretical model is established to predict the working concentration range of the method. Lead(II)-selective Celgard membranes were used here with H+ as the dominant interfering ions. The emf difference for stirred and unstirred solutions was measured, and the magnitude of this emf change as a function of the sample Pb2+ concentration was found to exhibit a bell shape that spans approximately 3 orders of magnitude. The concentration of interfering ions and the selectivity of the membrane were demonstrated to be important factors that affect the working range. Smaller ratios of primary ion concentrations at both aqueous sides of the membrane gave smaller emf difference values, and emf changes could still be observed with a logarithmic concentration ratio of 0.05. All experimental results correlated satisfactorily with the theoretical model.
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Affiliation(s)
- Wittaya Ngeontae
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, USA
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De Marco R, Clarke G, Pejcic B. Ion-Selective Electrode Potentiometry in Environmental Analysis. ELECTROANAL 2007. [DOI: 10.1002/elan.200703916] [Citation(s) in RCA: 195] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Abstract
For most chemists, potentiometry with ion-selective electrodes (ISEs) primarily means pH measurements with a glass electrode. Those interested in clinical analysis might know that ISEs, routinely used for the determination of blood electrolytes, have a market size comparable to that of glass electrodes. It is even less well known that potentiometry went through a silent revolution during the past decade. The lower detection limit and the discrimination of interfering ions (the selectivity coefficients) have been improved in many cases by factors up to 10(6) and 10(10), respectively, thus allowing their application in fields such as environmental trace analysis and potentiometric biosensing. The determination of complex formation constants for lipophilic hosts and ionic guests is also covered in this Minireview.
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Affiliation(s)
- Eric Bakker
- Prof. Eric Bakker, Department of Chemistry, Purdue University, West Lafayette, IN 47907, USA, E-mail:
| | - Ernö Pretsch
- Prof. Ernö Pretsch, Laboratorium für Organische Chemie, ETH Zürich, CH-8093 Zürich, Switzerland, E-mail:
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Abstract
During the last decade, the capabilities of potentiometric analysis have changed fundamentally in that the lower limit of detection (LOD) of ion-selective electrodes (ISEs) has improved by a factor of up to one million and the discrimination factor of interferences from ions by up to one billion. These spectacular improvements are related to the control of ion fluxes through the ion-selective membrane. Nowadays, ISEs can be used for trace measurements in environmental samples. However, by reducing the volume of the samples, the LOD in terms of the amount of analytes has been reduced to the attomole range. This is promising for bioanalysis using metal nanoparticle labels. Other recent progress includes the excellent fundamental understanding of the working mechanism, the introduction of a novel kind of calibration procedure that reduces the demands on signal stability and reproducibility, and the advent of pulsed amperometric methods.
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Affiliation(s)
- Ernö Pretsch
- Laboratory for Organic Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland, Tel.: +41 44 632 2926; Fax: +41 44 632 1164; E-mail:
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