Chromoionophore-Mediated Imaging of Water Transport in Ion-Selective Membranes

Zwickl, Titus; Schneider, Bernhard; Lindner, Ernő; Sokalski, Tomasz; Schaller, Ulrich; Pretsch, Ernö

doi:10.2116/analsci.14.57

Cited by 32 publications

(27 citation statements)

References 23 publications

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“…A later study by Zwickl et al using a water-sensitive lipophilic chromoionophore did not confirm the fast initial water uptake, but reported a single apparent water diffusion coefficient of ca. 2 Â 10 À8 cm 2 s À1 [28]. The fact that they did not observe light scattering due to water droplets seems to suggest that the use of hydrophilic indicators may indeed have altered the water uptake in these studies.…”

mentioning

confidence: 77%

“…As a first task to elucidate the effect of the water uptake by ISMs on the analytical performance characteristics of SC-ISEs, we have studied the water uptake of highly plasticized poly(vinyl chloride) (PVC) membranes, which are the most commonly used ISMs. Only a few papers published in the 1990s by Harrison et al [24 -27], Zwickl et al [28], Ye et al [29], as well as much later by Moczar et al [30], studied the water uptake of these membranes.…”

Section: Introductionmentioning

confidence: 99%

“…The best fitting to the experimental data was obtained with a mathematical model consisting of two diffusion coefficients describing fast and slow diffusion of water in the PVC membranes ( ) for a similar membrane composition [28]. However, it is possible that the sensitivity of the chromoionophore-mediated spectroscopic imaging used by Zwickl et al is not high enough to be able to detect the fast initial water uptake with probably rather low concentrations at least in the beginning of the equilibration process.…”

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confidence: 99%

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FTIR‐ATR Study of Water Uptake and Diffusion Through Ion‐Selective Membranes Based on Plasticized Poly(vinyl chloride)

et al. 2009

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In this paper, the water uptake and diffusion of water through ion-selective membranes based on plasticized poly(vinyl chloride) (PVC) have been studied by FTIR-ATR spectroscopy. The diffusion of water was modeled by the finite-difference method and the obtained diffusion coefficients are reported for membranes plasticized with bis(2-ethylhexyl) sebacate (DOS) and 2-nitrophenyl octyl ether (oNPOE). The influence of various common membrane additives such as lipophilic salts and ionophores on the water uptake was also determined through representative membrane formulations (potassium tetrakis [3,5-bis(trifluoromethyl)phenyl]borate (KTFPB) and/or calcium ionophore IV (ETH 5234)). The best fits of the time dependent water concentration changes in the membrane upon water uptake were obtained with a model consisting of two diffusion coefficients describing fast (ca. 1.5 Â 10 À7 cm 2 s À1) and slow (ca. 9.5 Â 10 À9 cm 2 s À1 ) diffusion of water in the PVC membranes. In contrast to the water uptake of the membranes, the diffusion rates were found to be practically independent of the membrane composition. It is shown that KTFPB and ETH 5234 decrease the water uptake whereas it is facilitated by a higher plasticizer content of the membrane. Monomeric, dimeric, clustered and bulk water could be distinguished by deconvolution of the FTIR-ATR spectra, which is important for understanding the water uptake mechanism.

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confidence: 77%

Section: Introductionmentioning

confidence: 99%

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confidence: 99%

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FTIR‐ATR Study of Water Uptake and Diffusion Through Ion‐Selective Membranes Based on Plasticized Poly(vinyl chloride)

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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.…”

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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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“…The concentration profiles of protonated and unprotonated forms of the chromoionophore were recorded in real-time at a nominal resolution of 2.25 lm (at 10-fold magnification of the microscope), which allowed for the first time the interpretation of potential transients on the basis of membrane composition changes. In addition, spectropotentiometry has been used for imaging the chro-moionophore-mediated water transport (24) and the optical determination of the diffusion coefficients of complexed and uncomplexed chromoionophores (22,23).…”

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

Gyurcsányi¹,

Lindner²

2006

Cytometry Pt A

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Background:High‐resolution spectroscopic imaging of the cross section of ion‐selective membranes during real‐time electrochemical measurements is termed spectroelectrochemical microscopy (SpECM). SpECM is aimed for optimizing the experimental conditions in mass transport controlled ion‐selective electrode (ISE) membranes for improved detection limit.Methods:The SpECM measurements are performed in a thin layer electrochemical cell. The key element of the cell is a membrane strip spacer ring assembly which forms a two compartment electrochemical cell. The cell is placed onto the stage of a microscope and the membrane strip is positioned in the center of the field of view. A slice of the image is focused onto the entrance slit of the imaging spectrometer.Results:SpECM has been used for the determination of the diffusion coefficients of different membrane ingredients and for the quantitative assessment of the charged site concentrations in ISE membranes and membrane plasticizers. In addition, changes in the concentration profiles of the ionophore (free and complexed) and charged mobile sites inside the ISE membranes are documented upon the application of large external voltages.Conclusions:This account demonstrates the power and advantages of SpECM, a multispectral imaging method for investigations of mass transport processes in ISE membranes during electrochemical measurements. © 2006 International Society for Analytical Cytology

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Chromoionophore-Mediated Imaging of Water Transport in Ion-Selective Membranes

Cited by 32 publications

References 23 publications

FTIR‐ATR Study of Water Uptake and Diffusion Through Ion‐Selective Membranes Based on Plasticized Poly(vinyl chloride)

FTIR‐ATR Study of Water Uptake and Diffusion Through Ion‐Selective Membranes Based on Plasticized Poly(vinyl chloride)

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

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

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