Ferrocene-modified horseradish peroxidase enzyme electrodes. A kinetic study on reactions with hydrogen peroxide and linoleic hydroperoxide

Abstract

An enzyme electrode for the determination of hydrogen peroxide and linoleic hydroperoxide, a model compound for lipid hydroperoxides, is described. Horseradish peroxidase bearing covalently attached ferrocene groups as electron transfer mediators is used as the sensing molecule and is adsorbed to the surface of disposable printed carbon electrodes as the base sensor. The electrodes are suitable for the determination of hydrogen peroxide in the range 1–50 µmol l^–1 and linoleic hydroperoxide in the range 5–100 µmol l^–1. A comparison of the kinetic behaviour of the modified enzyme in solution by spectrophotometry, and on the electrode by amperometry, shows that the catalytic current is limited by mass transport when hydrogen peroxide is the substrate and enzyme kinetics when linoleic hydroperoxide is the substrate.