Zugle Ruphino, Kambo-Dorsa James, Gadzekpo Victor Patrick Yao
Department of chemistry, University of Cape Coast, Cape Coast, Ghana.
Talanta. 2003 Dec 23;61(6):837-48. doi: 10.1016/S0039-9140(03)00377-1.
Gold electrodes were chemically modified with thioctic acid monolayer designed to mimic biological ion-channel membranes. The technique was then used in the determination of alkali, alkaline earth, thallium(I), and lanthanum metal cations as analytes. Cyclic voltammograms (CV) of Fe(CN)6 an electroactive marker, were measured in the presence of the various types of analyte cations. In the absence of the analyte cation, electrostatic repulsion between the marker anions and the carboxylate groups of the receptor monolayer hindered the approach of the marker anion to the electrode surface and hence hindered its reduction. The modified electrodes responded well to the metal cations except the alkali metal cations. The sensors could detect the trivalent cation La(3+) at concentrations as low as 10(-8) M. The response of the sensor to the metal cations increase in the order alkali metal<alkaline earth metal<lanthanum metal. As compared to divalent ions, the trivalent ion, La(3+) can be discriminated in the ratio 1:100. This makes it possible to determine the trivalent ion in a sample matrix containing monovalent and divalent cations. Thallium(I) ion showed marked deviation in its response as compared to monovalent ions of the alkali metals. The ion-channel sensor based on self-assembled monolayer of thioctic acid therefore offers a potential alternative technique for the selective determination of metal ions.
金电极用设计用于模拟生物离子通道膜的硫辛酸单分子层进行化学修饰。然后将该技术用于测定碱金属、碱土金属、铊（I）和镧等金属阳离子作为分析物。在存在各种类型分析物阳离子的情况下，测量了电活性标记物Fe(CN)6的循环伏安图（CV）。在不存在分析物阳离子时，标记物阴离子与受体单分子层的羧酸根基团之间的静电排斥阻碍了标记物阴离子接近电极表面，从而阻碍了其还原。修饰电极对除碱金属阳离子外的金属阳离子响应良好。该传感器能够检测低至10(-8) M浓度的三价阳离子La(3+)。传感器对金属阳离子的响应按碱金属<碱土金属<镧金属的顺序增加。与二价离子相比，三价离子La(3+)能够以1:100的比例被区分出来。这使得在含有单价和二价阳离子的样品基质中测定三价离子成为可能。铊（I）离子与碱金属的单价离子相比，其响应表现出明显偏差。因此，基于硫辛酸自组装单分子层的离子通道传感器为金属离子的选择性测定提供了一种潜在的替代技术。
