Lowering the Detection Limit of Solvent Polymeric Ion-Selective Membrane Electrodes. 2. Influence of Composition of Sample and Internal Electrolyte Solution

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• 作者：Tomasz Sokalski ; Alan Ceresa ; Monia Fibbioli ; Titus Zwickl ; Eric Bakker ; and Ernö ; Pretsch
• 刊名：Analytical Chemistry
• 出版年：1999
• 出版时间：March 15, 1999
• 年：1999
• 卷：71
• 期：6
• 页码：1210 - 1214
• 全文大小：76K
• 年卷期：v.71,no.6(March 15, 1999)
• ISSN：1520-6882

文摘

The influence of the composition of the internal electrolytesolution on the response of Pb²⁺- and Ca²⁺-selectivemembrane electrodes is investigated. It is shown that thelower detection limit is improved by generating, in themembrane, ionic gradients that lead to a flux of primaryions toward the inner reference electrolyte solution. If theion flux is too strong, it may cause analyte depletion atthe membrane surface and, as a consequence, apparentsuper-Nernstian response. Such electrodes are not adequate to measure low analyte activities but can be usedto determine unbiased selectivity factors. The results areinterpreted in terms of a steady-state model, introducedin the companion paper, that describes the influence ofconcentration gradients generated by ion-exchange andcoextraction processes on both sides of the membrane.