Effect of transmembrane electrolyte diffusion on the detection limit of carrier-based potentiometric ion sensors
Effect of transmembrane electrolyte diffusion on the detection limit of carrier-based potentiometric ion sensors
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DOI：
10.1021/ac970690y
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发表时间：
1998-01-15
影响因子：
7.4
通讯作者：
Bakker, E
中科院分区：
文献类型：
--
作者：
Mathison, S;Bakker, E
载体为基础的离子选择性电极的检测限的解释由存在的局部升高浓度的测量离子在样品膜相边界。由于离子选择性电极响应于相边界活动，因此这种升高的浓度使得电位传感器对稀释的本体浓度变化不敏感。可以想到用于从膜连续释放测量离子的不同机制。预计将内部电解质提取到离子选择性膜的背面中会导致跨膜的电解质浓度梯度，并因此导致从内部填充溶液到样品的测量离子的净nux。这种效果是由一个扩展的模型，尊重相关的提取和扩散过程。在背侧的coextraction的程度预测的基础上的电位测量的阴离子干扰的范围。发现这些预测与缬氨霉素电极的实验结果有很好的关系。发现内电解质中亲脂性阴离子的存在会增加检测限，这是由于增加了对膜的提取。显然存在上限，超过该上限，当增加内部灌装溶液浓度时，检测限不再增加。由于从膜表面到本体样品的质量传递增加，搅拌样品降低了检测限。
The detection limit of carrier-based ion-selective electrodes is explained by the presence of a locally elevated concentration of measuring ions at the sample-membrane phase boundary. Since ion-selective electrodes are responsive to phase boundary activities, such elevated concentrations render the potentiometric sensor insensitive to dilute bulk concentration changes. Different mechanisms for the continuous release of measuring ions from the membrane are conceivable. The extraction of inner electrolyte into the backside of the ion-selective membrane is predicted to lead to a concentration gradient of electrolyte across the membrane and therefore to a net nux of measuring ions from the inner filling solution to the sample. This effect is described by an extended model that respects the relevant extraction and diffusion processes. The extent of coextraction at the backside is predicted on the basis of potentiometric measurements on the range of anion interference. These predictions are found to relate well to experimental results with valino-mycin electrodes. The presence of lipophilic anions in the inner electrolyte is found to increase detection limits owing to the increased extraction into the membrane. An upper limit apparently exists beyond which the detection limit is no longer increased upon increasing the inner filling solution concentration. Stirring the sample decreases the detection limit owing to increased mass transport from the membrane surface to the bulk sample.