Department of Inorganic and Analytical Chemistry, University of Geneva, Quai E.-Ansermet 30, CH-1211 Geneva, Switzerland.
Anal Chem. 2013 Jul 2;85(13):6208-12. doi: 10.1021/ac400470n. Epub 2013 Jun 13.
Potentiometric sensors that exhibit a non-Hofmeister selectivity sequence are normally designed by selective chemical recognition elements in the membrane. In other situations, when used as detectors in separation science, for example, membranes that respond equally to most ions are preferred. With so-called liquid membranes, a low selectivity is difficult to accomplish since these membranes are intrinsically responsive to lipophilic species. Instead, the high solubility of sample lipids in an ionophore-free sensing matrix results in a deterioration of the response. We explore here potentiometric sensors on the basis of ion-exchange membranes commonly used in fuel cell applications and electrodialysis, which have so far not found their way into the field of ion-selective electrodes. These membranes act as Donnan exclusion membranes as the ions are not stripped of their hydration shell as they interact with the membrane. Because of this, lipophilic ions are no longer preferred over hydrophilic ones, making them promising candidates for the detection of abundant ions in the presence of lipophilic ones or as detectors in separation science. Two types of cation-exchanger membranes and one anion-exchange membrane were characterized, and potentiometric measuring ranges were found to be Nernstian over a wide range down to about 10 μM concentrations. Depending on the specific membrane, lipophilic ions gave equal response to hydrophilic ones or were even somewhat discriminated. The medium and long-term stability and reproducibility of the electrode signals were found to be promising when evaluated in synthetic and whole blood samples.
通常，表现出非霍夫迈斯特选择性序列的电位传感器是通过膜中的选择性化学识别元件设计的。在其他情况下，例如在分离科学中用作探测器时，优先选择对大多数离子响应相等的膜。对于所谓的液体膜，由于这些膜对亲脂性物质固有地有响应，因此很难实现低选择性。相反，由于样品脂质在无载体传感基质中的高溶解度导致响应恶化。我们在这里探索基于燃料电池应用和电渗析中常用的离子交换膜的电位传感器，迄今为止，这些传感器尚未进入离子选择性电极领域。这些膜作为唐南排斥膜起作用，因为当离子与膜相互作用时，它们不会失去其水合壳。由于这个原因，亲脂性离子不再优先于亲水性离子，这使它们成为在存在亲脂性离子的情况下检测丰富离子的有前途的候选者，或者作为分离科学中的探测器。两种类型的阳离子交换膜和一种阴离子交换膜进行了表征，发现其电位测量范围在很宽的范围内呈能斯特线性，直至约 10 μM 的浓度。根据特定的膜，亲脂性离子对亲水性离子的响应相等，或者甚至有些区分。在合成和全血样本中评估时，发现电极信号的中短期稳定性和重现性很有希望。
