SILICA SOL-GEL IMMOBILIZED AMPEROMETRIC BIOSENSOR FOR HYDROGEN-PEROXIDE

An amperometric enzyme electrode for hydrogen peroxide was developed v ia easy and effective enzyme immobilization using the sol-gel techniqu e. The enzyme electrode comprises horseradish peroxidase (HRP) immobil ized in the silica sol-gel matrix on a carbon paste electrode (CPE). H ydrogen peroxide was detected in the presence of hexacyanoferrate(II) as a mediator to transfer electrons between the electrode surface and hydrogen peroxide. The effects of operational parameters such as the o perating potential of the working electrode, mediator concentration an d pH, and thermal stability, were explored for optimum analytical perf ormance by using an amperometric method. Linear calibration for hydrog en peroxide was obtained in the range 2x10(-5) to 2.6x10(-3) M under t he optimized conditions. The apparent Michaelis-Menten constant of the enzyme electrode was 4.8 mM. The performance of this enzyme electrode was also investigated using flow-injection analysis. The enzyme elect rode retained about 60% of its activity after 35 days of storage in a phosphate buffer at 4 degrees C.