Quantification of the concentration of ionic impurities in polymeric sensing membranes with the segmented sandwich technique.
Quantification of the concentration of ionic impurities in polymeric sensing membranes with the segmented sandwich technique.
复制标题
使用分段夹心技术定量聚合物传感膜中离子杂质的浓度。
DOI：
10.1021/ac0104126
复制
发表时间：
2001
影响因子：
7.4
通讯作者：
Bakker,E
中科院分区：
文献类型：
--
作者：
Qin,Y;Bakker,E
溶剂型聚合物膜中的离子杂质是早期没有添加离子交换剂的离子选择电极(ISES)表现出功能电位响应的主要原因。今天，对于设计具有低检测下限和伏安离子选择电极、延长工作寿命和优化传感选择性的离子选择电极而言，了解此类杂质及其消除变得重要。本文采用电位法分段夹心膜技术直接研究了膜相中杂质的含量和性质。这项技术可以用于许多离子载体和不同的膜基质，不需要专门的设备。在含有弱结合钾离子载体的膜中，聚氯乙烯−DOS(双(2-乙基己基)癸酸酯)和聚氯乙烯−NPOE(邻硝基苯基苯基醚)中的阴离子杂质浓度约为100molmoL/kg。羧化聚氯乙烯−的阳离子交换中心浓度较高(1.62mmoL/kg)。在两段膜中加入中性亲脂性盐ETH500对聚氯乙烯−膜的测定结果影响不大，但对聚氯乙烯−膜的膜电位有较大影响。理论解释说，将这种盐添加到以离子配对为主的膜中，对于用这项技术准确评估离子杂质是必不可少的。
Ionic impurities in solvent polymeric membranes have been the main reason early ion-selective electrodes (ISEs) without added ion exchanger exhibited a functional potentiometric response. Today, knowledge of such impurities and their elimination becomes important in view of designing ISEs with low detection limits and voltammetric ion-selective electrodes, to increase operational lifetime, and to optimize sensing selectivity. Here, a potentiometric segmented sandwich membrane technique is used to study the amount and properties of impurities in situ directly in the membrane phase. This technique can be used with a number of ionophores and with different membrane matrixes and does not require specialized equipment. The concentration of anionic impurities in PVC−DOS (bis(2-ethylhexyl) sebacate) and PVC−NPOE (o-nitrophenyloctyl ether) was found to be on the order of 100 μmol/kg with membranes containing weakly binding potassium ionophores. The concentration of cation-exchanger sites of carboxylated PVC−NPOE was found to be higher (1.62 mmol/kg). Addition of the neutral lipophilic salt ETH 500 to both membrane segments had only a marginal effect on the results for PVC−NPOE membranes but had a large impact on the observed membrane potential for PVC−DOS membranes. Theory explains that the addition of such salt to membranes where ion pairing is predominant is essential for the accurate assessment of ionic impurities with this technique.