Limitations of current polarization for lowering the detection limit of potentiometric polymeric membrane sensors.
Limitations of current polarization for lowering the detection limit of potentiometric polymeric membrane sensors.
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DOI：
10.1021/ac802588j
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发表时间：
2009-05-01
影响因子：
7.4
通讯作者：
Pretsch, Ernoe
中科院分区：
文献类型：
--
作者：
Hoefler, Lajos;Bedlechowicz, Iwona;Vigassy, Tamas;Gyurcsanyi, Robert E.;Bakker, Eric;Pretsch, Ernoe
通过聚合物离子选择性膜的离子通量是决定电位离子传感器检测下限的决定性参数。较早时提出了施加电流来抵消这种通量，并将检测限降低到超痕量水平。然而，到目前为止，该方法尚未在实际情况中使用，因为正确的电流幅度需要样品成分的先验知识。本文从理论和实验两方面探讨了利用搅拌效应来确定最佳电流的方法。它表明，传统上使用的稳态模型假设均匀分布的离子交换剂在膜中，固定的时间，违反电中性条件。引入了一种改进的稳态模型，该模型允许离子交换剂的浓度倾斜，并预测搅拌效应确实可以用来找到最佳电流。理想情况下，通过选择最佳电流和非常长的测量时间，可以获得热力学检测限。然而，在实践中，搅拌效果在低浓度下下降，并且条件远离稳定状态。因此，通过恒电流控制可实现的检测下限的改进仅为大约一个数量级。一个数值有限差分近似示出跟踪的实验电位响应的银选择性电极，并充分再现搅拌效果，即使对于不同的空调协议。搅拌效应已成功用于提高内溶液优化不良的电极的检测限，然而，超出化学优化通常可行范围的显着改进似乎并不容易实现。结果表明，与传统的膜的可能性，提高检测限的电流极化是远远有限的比假设到目前为止。
Ion fluxes across polymeric ion-selective membranes are a decisive parameter dictating the lower detection limit of potentiometric ion sensors. An applied current was earlier proposed to counteract such fluxes and reduce the detection limit to ultra-trace levels. So far, however, the method has not been used in practical situations since the correct current amplitude requires prior knowledge of the sample composition. This paper explores the use of the stir effect to evaluate the optimal current by theory and experiments. It is shown that the traditionally used steady-state model assuming a uniform distribution of ion exchanger in the membrane, fixed with time, violates the electroneutrality condition. A modified steady-state model is introduced that allows for a concentration tilt of the ion exchanger and predicts that a stir effect can indeed be utilized to find the optimal current. Ideally, by choosing the optimal current and very long measurement times, the thermodynamic detection limit might be obtained. However, in practice the stir effect declines at low concentrations and the conditions are far from steady state. Therefore, the improvement of the lower detection limit achievable by galvanostatic control is only about one order of magnitude. A numerical finite-difference approximation is shown to trace the experimental potential responses of silver-selective electrodes well, and to reproduce the stir effect adequately, even for different conditioning protocols. The stir effect is successfully used to improve the detection limit of electrodes with ill-optimized inner solutions, however, significant improvements beyond what is commonly feasible by chemical optimization does not seem to be easily achievable. The results indicate that with conventional membranes the possibility of improving the detection limit by current polarization is much more limited than assumed so far.
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影响因子：
7.4
作者：
Malon, Adam;Bakker, Eric;Pretsch, Ernoe
通讯作者：
Pretsch, Ernoe
影响因子：
7.4
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4.5
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Morf, WE;Badertscher, M;Pretsch, E
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作者：
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通讯作者：
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4.5
作者：
Ceresa, A;Sokalski, T;Pretsch, E
通讯作者：
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