Egorov V V, Rakhman'ko E M, Okaev E B, Pomelenok E V, Nazarov V A
Institute for Physical and Chemical Problems of the Belarussian State University, Leningradskaja Str. 14, 220080 Minsk, Belarus.
Talanta. 2004 May 10;63(1):119-30. doi: 10.1016/j.talanta.2003.11.019.
It has been found experimentally and substantiated theoretically that the anion-exchange selectivity in water-lipophilic quaternary ammonium salts (QAS) toluene solutions systems as well as the potentiometric selectivity of plasticized PVC membranes containing QAS, are strongly influenced by ion association. In particular, it has been demonstrated that varying the steric accessibility of QAS exchange center is a powerful tool for the selectivity control. The experimental values of the selectivity change caused by variations in the QAS exchange center steric accessibility were about 3 orders of magnitude when the single-charged ions were exchanged for the single-charged ones and more than seven orders when double-charged ions were exchanged for the single-charged. The above effects have also been observed for the potentiometric selectivity of QAS-based PVC membranes and, to some extent, for the potentiometric selectivity of the neutral anion carrier-based membranes doped by QAS to provide anion permselectivity. This fact is of immediate practical interest for the development of ISE with improved selectivity. The obtained results allow to revise the generally accepted idea of QAS as "nonselective" ion-exchangers and to suggest specific ways for controlling the ion-exchange and potentiometric selectivity using the ion association as a tool.
实验发现并经理论证实，在水 - 亲脂性季铵盐（QAS） - 甲苯溶液体系中的阴离子交换选择性以及含有QAS的增塑PVC膜的电位选择性，均受到离子缔合的强烈影响。特别是，已证明改变QAS交换中心的空间可及性是控制选择性的有力工具。当单电荷离子与单电荷离子交换时，由QAS交换中心空间可及性变化引起的选择性变化的实验值约为3个数量级；当双电荷离子与单电荷离子交换时，则超过7个数量级。对于基于QAS的PVC膜的电位选择性以及在一定程度上对于由QAS掺杂以提供阴离子选择透过性的基于中性阴离子载体的膜的电位选择性，也观察到了上述效应。这一事实对于开发具有更高选择性的离子选择性电极具有直接的实际意义。所获得的结果允许修正关于QAS作为“非选择性”离子交换剂的普遍接受的观念，并提出以离子缔合为工具控制离子交换和电位选择性的具体方法。
