Electrochemical methods for the determination of the diffusion coefficient of ionophores and ionophore–ion complexes in plasticized PVC membranes
| Autor: | Ernő Lindner, Klára Tóth, Sándor Bodor, Justin M. Zook, Róbert E. Gyurcsányi |
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| Rok vydání: | 2008 |
| Předmět: |
Ions
Ion Transport Ionophores Chemistry Potentiometric titration Analytical chemistry Ionophore Membranes Artificial Chronoamperometry Electrochemistry Biochemistry Analytical Chemistry Ion selective electrode Diffusion Polyvinyl chloride chemistry.chemical_compound Membrane Plasticizers Humans Environmental Chemistry Polyvinyl Chloride Polarization (electrochemistry) Ion-Selective Electrodes Spectroscopy |
| Zdroj: | The Analyst. 133:635 |
| ISSN: | 1364-5528 0003-2654 |
| DOI: | 10.1039/b718110h |
| Popis: | The diffusion coefficients of active components in ion-selective membranes have a decisive influence on the life-time and detection limit of the respective ion-selective electrodes, as well as influencing the rate of polarization and relaxation processes of electrically perturbed ion sensors. Therefore, the rational design of mass transport controlled ion-selective electrodes with sub-nanomolar detection limits requires reliable data on the diffusion coefficients. We have implemented electrochemical methods for the quantitative assessment of both the diffusion coefficients of free ionophores and ion-ionophore complexes. The diffusion coefficients of the pH-sensitive chromoionophore ETH 5294 and the calcium-selective ionophore ETH 5234 were determined in plasticized PVC membranes with different PVC to plasticizer ratios. The diffusion coefficient of the free chromoionophore determined by a chronoamperometric method was validated with optical methods for a variety of membrane compositions. The calcium-selective ionophore ETH 5234 was used as a model compound to assess the diffusion coefficient of the ion-ionophore complex calculated from the time required for the complexes to cross a freshly prepared membrane during potentiometric ion-breakthrough experiments. The difference between the diffusion coefficients of the free ionophore ETH 5234 and the ion-ionophore complex was found to be significant and correlated well with the geometry of the respective species. |
| Databáze: | OpenAIRE |
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