Analytical Sciences

Amperometric Sensor for Hydrogen Peroxide Based on Immobilized Cytochrome c on Binary Self-assembled Monolayers

Xueping JI* and Toshio NAKAMURA**

*Department of Medical Chemistry, Hebei Medical University, Shijiazhuang 050017, China
**Department of Chemistry, Faculty of Science, Shinshu University, Matsumoto 390-8621, Japan

A sensitive sensor for the determination of hydrogen peroxide (H₂O₂) was fabricated by immobilizing cytochrome c (cyt c) on binary self-assembled monolayers (SAMs) of 5-(1,2-dithiolan-3-yl)valeric acid (thioctic acid, T-COOH) and 5-(1,2-dithiolan-3-yl)valeramide (thioctic acid amide, T-NH₂) on gold electrodes. The electrochemical characteristics of immobilized cyt c were investigated by cyclic voltammetry, electrochemical impedance spectroscopy and chronoamperometry. The modified electrode showed good electrocatalytic activity towards the reduction of H₂O₂. The catalytic current is linear with the H₂O₂ concentration ranging from 10.0 to 300 µM with a correlation coefficient of 0.9996. The apparent Michaelis-Menten constant (K_m^app) was found to be 619 µM. The sensor achieved 95% of the steady-state current within 10 s, exhibiting high sensitivity (1.7 nA µM^-1 cm^-2).

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