Department of Inorganic and Analytical Chemistry, University of Geneva , Quai Ernest-Ansermet 30, CH-1211 Geneva, Switzerland.
Anal Chem. 2016 Feb 2;88(3):1654-60. doi: 10.1021/acs.analchem.5b03611. Epub 2016 Jan 8.
As shown in recent work, thin layer ion-selective multi-ionophore membranes can be interrogated by cyclic voltammetry to detect the ion activity of multiple species simultaneously and selectively. Additional fundamental evidence is put forward on ion discrimination with thin multi-ionophore-based membranes with thicknesses of 200 ± 25 nm and backside contacted with poly-3-octylthiophene (POT). An anodic potential scan partially oxidizes the POT film (to POT(+)), thereby initiating the release of hydrophilic cations from the membrane phase to the sample solution at a characteristic potential. Varying concentration of added cation-exchanger demonstrates that it limits the ion transfer charge and not the deposited POT film. Voltammograms with multiple peaks are observed with each associated with the transfer of one type of ion (lithium, potassium, and sodium). Experimental conditions (thickness and composition of the membrane and concentration of the sample) are chosen that allow one to describe the system by a thermodynamic rather than kinetic model. As a consequence, apparent stability constants for sodium, potassium, and lithium (assuming 1:1 stoichiometry) with their respective ionophores are calculated and agree well with the values obtained by the potentiometric sandwich membrane technique. As an analytical application, a membrane containing three ionophores was used to determine lithium, sodium, and potassium in artificial samples at the same location and within a single voltammetric scan. Lithium and potassium were also determined in undiluted human plasma in the therapeutic concentration range.
如最近的工作所示，薄层层析型多离子载体膜可以通过循环伏安法进行检测，以同时和选择性地检测多种物质的离子活性。此外，还提出了关于具有 200 ± 25nm 厚度的基于多离子载体的薄膜和背面与聚-3-辛基噻吩 (POT) 接触的离子选择性的基本证据。阳极电势扫描部分氧化 POT 膜（至 POT(+)），从而在特征电势下从膜相开始向样品溶液释放亲水性阳离子。添加的阳离子交换剂的浓度变化表明，它限制了离子转移电荷，而不是沉积的 POT 膜。观察到具有多个峰的伏安图，每个峰都与一种离子（锂、钾和钠）的转移有关。选择实验条件（膜的厚度和组成以及样品的浓度），以便用热力学而不是动力学模型来描述系统。因此，计算出与各自离子载体的钠离子、钾离子和锂离子（假设为 1:1 化学计量比）的表观稳定常数，并与通过电位夹层膜技术获得的值吻合良好。作为分析应用，在同一位置和单个伏安扫描中，使用含有三种离子载体的膜来测定人工样品中的锂、钠和钾。在治疗浓度范围内，还测定了未经稀释的人血浆中的锂和钾。
