School of Chemistry and ARC Centre for Green Chemistry, Monash University, Clayton, Victoria, 3800, Australia.
Anal Chem. 2010 Mar 1;82(5):1624-33. doi: 10.1021/ac902296r.
A general theory has been developed for voltammetric ion sensing of cations and anions based on the use of an electrode coated with a membrane containing an electroactive species, an ionophore, and a supporting electrolyte dissolved in a plasticizer. In experimental studies, a membrane coated electrode is fabricated by the drop coating method. In one configuration, a glassy carbon electrode is coated with a poly(vinyl chloride) based membrane, which contains the electroactive species, ionophore, plasticizer and supporting electrolyte. In the case of a cation sensor, ionophore facilitated transfer of the target cation from the aqueous solution to the membrane phase occurs during the course of the reduction of the electroactive species present in the membrane in order to maintain charge neutrality. The formal potential is calculated from the cyclic voltammogram as the average of the reduction and oxidation peak potentials and depends on the identity and concentration of the ion present in the aqueous solution phase. A plot of the formal potential versus the logarithm of the concentration exhibits a close to Nernstian slope of RT/F millivolts per decade change in concentration when the concentration of K(+) and Na(+) is varied over the concentration range of 0.1 mM to 1 M when K(+) or Na(+) ionophores are used in the membrane. The slope is close to RT/2F millivolts for a Ca(2+) voltammetric ion-selective electrode fabricated using a Ca(2+) ionophore. The sensor measurement time is only a few seconds. Voltammetric sensors for K(+), Na(+), and Ca(2+) constructed in this manner exhibit the sensitivity and selectivity required for determination of these ions in environmentally and biologically important matrixes. Analogous principles apply to the fabrication of anion voltammetric sensors.
已经开发出一种基于使用涂有包含电活性物质、离子载体和溶解在增塑剂中的支持电解质的膜的电极的阳离子和阴离子伏安离子传感的通用理论。在实验研究中，通过滴涂法制备涂覆有膜的电极。在一种构型中，用基于聚氯乙烯的膜涂覆玻璃碳电极，该膜包含电活性物质、离子载体、增塑剂和支持电解质。在阳离子传感器的情况下，在膜中存在的电活性物质的还原过程中，离子载体促进目标阳离子从水溶液转移到膜相，以保持电荷中性。将形式电势从循环伏安图中计算为还原和氧化峰电势的平均值，并且取决于水溶液相中存在的离子的身份和浓度。当使用 K(+)或 Na(+)离子载体在膜中时，形式电势与浓度的对数的关系图显示出接近 Nernstian 的斜率，即在 0.1 mM 至 1 M 的浓度范围内，K(+)和 Na(+)的浓度变化时，斜率为 RT/F 毫伏/每 decade 浓度变化。使用 Ca(2+)离子载体制造的 Ca(2+)伏安离子选择性电极的斜率接近 RT/2F 毫伏。传感器测量时间仅为数秒。以这种方式构造的 K(+)、Na(+)和 Ca(2+)伏安传感器表现出在环境和生物上重要的基质中测定这些离子所需的灵敏度和选择性。类似的原理适用于阴离子伏安传感器的制造。
