Analytical Sciences

Self-Assembled Monolayer-Based Electrodes for Selective Determination of Cu²⁺ and Ag⁺ Ions with Antifouling Activity against Protein Adsorption

Tsutomu NAGAOKA * , Zhidong CHEN, Hiroyuki OKUNO, Masaharu NAKAYAMA and Kotaro OGURA

Department of Applied Chemistry, Faculty of Engineering, Yamaguchi University, Tokiwadai, Ube 755-8611, Japan

Self-assembled monolayers consisting of 3,3'-thiodipropionic acid and n-decyl mercaptan formed on gold electrodes have been studied for sensitive and selective determination of Cu²⁺ and Ag⁺ ions. The monolayers were found to provide both superior sensitivities and stabilities even in the presence of protein. Various factors, such as solution pH and concentration time, were optimized to obtain detection limits of 2x10^-9 M and 6x10^-8 M for Cu²⁺ and Ag⁺ ions at an S/N ratio of 2 by linear-sweep anodic stripping voltammetry. In the presence of albumin, the currents of the modified electrode, 1.75 times as great as those for the bare electrode, show a significant performance improvement over the previously reported cellulose coated electrode (1.13 times). One of the main advantages of using this electrode is an excellent antifouling activity against protein adsorption, coupled with highly selective metal-ion suppression/concentration capabilities, which can be attained without using a mercury film for preconcentration. (Keywords: Self-assembled electrode, heavy metal ion determination, protein adsorption, antifouling activity)

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