Immobilization of horseradish peroxidase on a self-assembled monolayer modified gold electrode for the detection of hydrogen peroxide

Abstract

A procedure for developing an enzyme electrode is described, based on the covalent binding of horseradish peroxidase to a self-assembled monolayer on a gold electrode. The resulting electrode exhibits high sensitivity (0.32 Al mol^–1 cm^–2) to hydrogen peroxide in the presence of a mediator (catechol). The current responses of the electrode are related to the concentrations of both substrate and mediator. The enzyme electrode responds well to hydrogen peroxide in the pH range 5.0–8.0. The optimum pH of the solution for the enzyme electrode is 6.0. Voltammetric experiments showed that the linear range of the enzyme electrode to hydrogen peroxide is from 1.0 µM to 1.0 mM and the detection limit is down to 0.5 µM. A decrease in current response is observed as the concentration of hydrogen peroxide increases above 6.0 mM, which might be due to the deactivation of the enzyme electrode at high concentrations of the substrate.