Ceresa Alan, Radu Aleksandar, Peper Shane, Bakker Eric, Pretsch Ernö
Laboratonum für Organische Chemie, ETH Hönggerberg, Zürich, Switzerland.
Anal Chem. 2002 Aug 15;74(16):4027-36. doi: 10.1021/ac025548y.
Submicromolar to picomolar lower detection limits have recently been obtained with various polymer membrane ion-selective electrodes by minimizing biases due to ion fluxes through the membrane. For the best performance, the compositions of the membrane and inner solution should be optimized for each application. Given the number of parameters to be adjusted, it has been difficult to find the best parameters for a target sample. In this paper, a much simplified and more practical steady-state model of zero-current ion fluxes is derived, which is based on measurable parameters. The model allows one to predict achievable lower detection limits for a membrane with given selectivities. It can also be used to predict the optimal composition of the inner filling solution for the measurement of samples with a known, typical ionic background. Selectivity coefficients of monovalent and divalent analyte ions required for desired detection limits in drinking water are calculated. As an application of the proposed general recipe, a silver-selective electrode is developed on the basis of the ionophore O,O''-bis[2-(methylthio)ethyl]-tert-butylcalix[4]arene. With the predicted optimal composition of the inner electrolyte, its lower detection limit is found to be 10(-9) M or 100 ppt Ag+ with an ionic background of 10(-5) M LiNO3, which is very close to the expected value.
最近，通过最小化因离子透过膜的通量所导致的偏差，各种聚合物膜离子选择电极已实现了亚微摩尔至皮摩尔的较低检测限。为实现最佳性能，应针对每种应用优化膜和内溶液的组成。鉴于需要调整的参数数量众多，很难找到针对目标样品的最佳参数。本文推导了一个基于可测量参数的、更为简化且更实用的零电流离子通量稳态模型。该模型能够预测具有给定选择性的膜可实现的较低检测限。它还可用于预测在测量具有已知典型离子背景的样品时内填充溶液的最佳组成。计算了饮用水中达到所需检测限所需的一价和二价分析物离子的选择性系数。作为所提出的通用方法的应用，基于离子载体O,O''-双[2-(甲硫基)乙基]-叔丁基杯[4]芳烃开发了一种银选择性电极。在内电解质的预测最佳组成下，发现其较低检测限为10(-9) M或100 ppt Ag+，离子背景为10(-5) M LiNO3，这与预期值非常接近。
