Dynamic diffusion model for tracing the real-tune potential response of polymeric membrane ion-selective electrodes
Dynamic diffusion model for tracing the real-tune potential response of polymeric membrane ion-selective electrodes
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DOI：
10.1021/ac049348t
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发表时间：
2004-11-01
影响因子：
7.4
通讯作者：
Bakker, E
中科院分区：
文献类型：
--
作者：
Radu, A;Meir, AJ;Bakker, E
提出了一种预测聚合物基离子选择电极（ISE）随时间变化的电位响应的数值解。该模型解决了依赖于水样品和有机膜相浓度梯度变化的短期和中期潜在漂移。这项工作对于理解具有低检测限和非经典超能斯蒂响应斜率的电位传感器的实时响应行为具有重要意义。作为一个模型系统，对含有银离子载体O，O"-双[2-（甲基硫）乙基]-叔丁基杯[4]芳烃的膜的初始暴露进行了监测，并将观察到的大的潜在漂移与理论预测进行了比较。该模型基于水扩散层和有机扩散层扩散方程的近似解，采用数值格式（时间有限差分和空间有限单元）。该模型可以在实验可用参数的基础上进行评估，并给出以前用更简单的稳态扩散模型无法获得的时间相关信息。对于所研究的案例，该模型给出了与实验数据非常好的相关性，尽管有机相的扩散系数低于预期。该模型可以解决关于低检测限离子选择电极和其他膜电极的响应时间和记忆效应的许多开放问题，其中离子通量是相关的。
A numerical solution for the prediction of the time-dependent potential response of a polymeric-based ion-selective electrode (ISE) is presented. The model addresses short- and middle-term potential drifts that are dependent on changes in concentration gradients in the aqueous sample and organic membrane phase. This work has important implications for the understanding of the real-time response behavior of potentiometric sensors with low detection limits and with nonclassical super-Nernstian response slopes. As a model system, the initial exposure of membranes containing the well-examined silver ionophore O,O"-bis[2-(methylthio)ethyl]-tert-butylcalix[4]arene was monitored, and the large observed potential drifts were compared to theoretical predictions. The model is based on an approximate solution of the diffusion equation for both aqueous and organic diffusion layers using a numerical scheme (finite difference in time and finite elements in space). The model may be evaluated on the basis of experimentally available parameters and gives time-dependent information previously inaccessible with a simpler steady-state diffusion model. For the cases studied, the model gave a very good correlation with experimental data, albeit with lower than expected diffusion coefficients for the organic phase. This model may address numerous open questions regarding the response time and memory effects of low-detection-limit ion-selective electrodes and for other membrane electrodes where ion fluxes are relevant.