SILICA SOL-GEL IMMOBILIZED AMPEROMETRIC ENZYME ELECTRODE FOR PEROXIDEDETERMINATION IN THE ORGANIC-PHASE

An amperometric enzyme electrode for peroxide determination in non-aqu eous media has been constructed by the silica sol-gel immobilization o f horseradish peroxidase (HRP) on a carbon paste electrode. Peroxides have been detected in the presence of ferrocene as the mediator in the organic phase to transfer electrons between the electrode surface and peroxides. The fabrication procedure of the enzyme electrode based on a sol-gel thin film derived from tetramethoxysilane has been optimize d. The effect of operational parameters, such as different organic sol vents, the amount of aqueous buffer in the organic solvent, mediator c oncentration and holding potential have been explored for the optimum analytical performance of the electrode. The electrode prepared using this immobilization technique has an excellent stability in some organ ic solvents, including methanol, acetonitrile and 2-propanol. The tren d in the sensitivity of different peroxides is as follows: H2O2 > laur oyl peroxide > butanone peroxide > tertbutyl-hydroperoxide. The appare nt Michaelis-Menten constants (K-m(app)) Of th, electrode in methanol for the above peroxides have been calculated. Applicability of the enz yme electrode for the measurement of hydrogen peroxide in real samples has been demonstrated. The results obtained by this electrode corrobo rate very well with the classical iodometric titration method for the determination of hydrogen peroxide. (C) 1998 Elsevier Science S.A. All rights reserved.