Multispectral imaging of ion transport in neutral carrier‐based cation‐selective membranes

Gyurcsányi, Róbert E.; Lindner, Ernő

doi:10.1002/cyto.a.20276

Cited by 17 publications

(14 citation statements)

References 49 publications

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“…In this method, a relatively large voltage is applied across the membrane. The applied voltage tilts the concentration profiles of the free ionophore, the ion-ionophore complex, and the mobile sites within the membrane [12], and it eventually forces the free ionophore concentration close to zero at one of the membrane boundaries [13]. When the concentration approaches zero, the current decays quickly in a Cottrellian manner [14], which results in a breakpoint (change in slope) in the chronoamperometric transients.…”

Section: Introductionmentioning

confidence: 99%

Mathematical Model of Current‐Polarized Ionophore‐Based Ion‐Selective Membranes: Large Current Chronopotentiometry

et al. 2008

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The properties of ionophore-based ion-selective membranes were investigated theoretically and experimentally for the first time in large-current chronopotentiometric experiments. In these experiments, when either the free ionophore or the ion-ionophore complex concentration drops to zero at one of the membrane boundaries, a characteristic drop in voltage (breakpoint) appears in the chronopotentiometric transients at a transition time t.Based on a mathematical model of current polarized membranes, theoretical equations were derived and tested. These equations describe the correlation between the transition time t and the concentration of free ionophore, the concentration of ion-ionophore complex, and the diffusion coefficients of species in the membrane. The simulated concentration profiles correlated well with concentration profiles recorded experimentally prior to the transition time using spectroelectrochemical microscopy (SpECM). Diffusion coefficients calculated from (i) the transition times, (ii) curve fitting, and (iii) the initial ohmic resistance of the studied membranes were also compared. Similar to chronoamperometry, the chronopotentiometric transition times provided possibilities for assessing the loss of free ionophore and lipophilic anion from cation selective electrode membranes during continuous use.

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Section: Introductionmentioning

confidence: 99%

Mathematical Model of Current‐Polarized Ionophore‐Based Ion‐Selective Membranes: Large Current Chronopotentiometry

et al. 2008

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“…One of the breakpoints can be correlated to the concentration polarization of the free ionophore while the other is correlated to the concentration polarization of the ion-ionophore complex. To verify the correlation between the breakpoint times and the times when the concentrations of the free and the complexed ionophores approach zero concentration (the zero concentration times) at the opposite membrane boundaries, spectroelectrochemical microscopy (SpECM) has been used in this work [8–10]. SpECM is a technique that allows the simultaneous measurement of the voltage transient and the concentration profiles of the free and complexed ionophores (chromoionophores) inside the membrane [7, 9].…”

Section: Introductionmentioning

confidence: 99%

Interpretation of chronopotentiometric transients of ion-selective membranes with two transition times

Zook

Bodor

Gyurcsányi

et al. 2010

Journal of Electroanalytical Chemistry

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Passing currents through ion-selective membranes has contributed to the development of a variety of novel methods. In this work, chronopotentiometric (CP) transients with two transition times (breakpoints) are presented for the first time, with the theoretical interpretation of such voltage transients. The validity of our theory has been confirmed in experiments utilizing ETH 5294 chromoionophore-based pH sensitive membranes with and without lipophilic background electrolyte and ETH 5234 ionophore-based calcium selective membranes in which the ionophore forms 3:1 complexes with Ca 2+ ions. The conditions under which two breakpoints can be identified in the chronopotentiometric voltage transients are discussed.Spectroelectrochemical microscopy (SpECM) is used to show that the two breakpoints in the CP curves emerge approximately when the free ionophore and ion-ionophore complex concentrations approach zero at the opposite membrane-solution interfaces. The two breakpoint times can be utilized to follow simultaneously the concentration changes of the free ionophore, the ion-ionophore complex, and the mobile anionic sites in cation-selective membranes. In membranes with known composition, the time instances where breakpoints occur can be used to estimate the free ionophore and the ion-ionophore complex diffusion coefficients.

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“…[18][19][20][21] The role of the SC is to provide a stable inner phase boundary potential 20,22,23 at the substrate/SC and SC/ISM interfaces, and to prevent the aqueous layer formation at the inner interface, which coupled to diffusion of ionic species within the ISM may lead to potential instability. 24 As all ISMs exhibit water uptake [25][26][27][28][29][30][31] , the prevention of the aqueous layer formation 32,33 with ill-defined ion activity has proven to be a major challenge.…”

mentioning

confidence: 99%

Pre-Polarized Hydrophobic Conducting Polymer Solid-Contact Ion-Selective Electrodes with Improved Potential Reproducibility

Papp

Lindfors

et al. 2017

Anal. Chem.

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Electrically conducting polymers (ECPs) are one of the most popular types of materials to interface ion-selective membranes (ISMs) with electron conducting substrates to construct solid contact ion-selective electrodes (SCISEs). For optimal ion-to-electron transduction and potential stability, the p-doped ECPs with low oxidation potentials such as PPy need to be generally in their conducting form along with providing a sufficiently hydrophobic interface to counteract the aqueous layer formation. The first criterion requires that the ECPs are in their oxidized state, but the high charge density of this state is detrimental for the prevention of the aqueous layer formation. We offer here a solution to this paradox by implementing a highly hydrophobic perfluorinated anion (perfluorooctane sulfonate, PFOS -) as doping ion by 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 which the oxidized form of the ECP becomes hydrophobic. The proof of concept is shown by using polypyrrole (PPy) films doped with PFOS -(PPy-PFOS) as the solid contact in K + -selective SCISEs (K + -SCISE). Prior to applying the plasticized poly(vinyl chloride) ISM, the oxidation state of the electrodeposited PPy-PFOS was adjusted by polarization to the known open circuit potential of the solid contact in 0.1 M KCl. We show that the pre-polarization results in a hydrophobic PPy-PFOS film with a water contact angle of 97±5º, which effectively prevents the aqueous layer formation under the ISM. Under optimal conditions the K + -SCISEs had a very low standard deviation of E 0 of only 501.0±0.7 mV that is the best E 0 reproducibility reported for ECP-based SCISEs.

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Multispectral imaging of ion transport in neutral carrier‐based cation‐selective membranes

Cited by 17 publications

References 49 publications

Mathematical Model of Current‐Polarized Ionophore‐Based Ion‐Selective Membranes: Large Current Chronopotentiometry

Mathematical Model of Current‐Polarized Ionophore‐Based Ion‐Selective Membranes: Large Current Chronopotentiometry

Interpretation of chronopotentiometric transients of ion-selective membranes with two transition times

Pre-Polarized Hydrophobic Conducting Polymer Solid-Contact Ion-Selective Electrodes with Improved Potential Reproducibility

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