An Anomalous Behavior of Anion-Exchange Membranes with Low Concentration of Quaternary Ammonium Sites: An Apparent Selectivity to Bicarbonate and Phosphate, and Its True Nature
✍ Scribed by Alexander L. Grekovich; Konstantin N. Mikhelson
- Publisher
- John Wiley and Sons
- Year
- 2002
- Tongue
- English
- Weight
- 99 KB
- Volume
- 14
- Category
- Article
- ISSN
- 1040-0397
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✦ Synopsis
It is shown that anion-selective electrodes with low concentration of quaternary ammonium sites exhibit an apparent response and selectivity to HCO 3 À and HPO 4 2À ions in aqueous solutions. It is, however, detected that none of these ions is the potential-determining, and the electrodes actually respond to OH À . The selectivity to OH À is due to unidentified anionic impurities in the plasticizer, and vanishes with aging of the electrodes. Additional purification of the plasticizer eliminates the selectivity to OH À , which, however, is restored after intentional addition of negatively charged sites. Quaternary ammonium sites with longer alkyl chains provide higher selectivity to OH À suggesting that this selectivity originates from steric hindrances against bigger anions.