A KINETIC-MODEL FOR THE ELECTROENZYMATIC PROCESSES INVOLVED IN POLYPHENOL-OXIDASE-BASED AMPEROMETRIC CATECHOL SENSORS

A kinetic model is presented for the electroenzymatic processes occurr ing at a polyphenol oxidase rotating-disk-bioelectrode for low concent rations of catechol. The work presented here is based on the same form alism as that previously used by Bartlett and Whitaker (J. Electroanal . Chem., 224 (1987) 27) for a glucose sensor. Our model allows one to analyze the effect of enzyme loading, film thickness, permeability and electrode rotation rate. It also unambiguously demonstrates for the f irst time that the high sensitivity and low detection limit observed f or such an enzymatic electrode is the consequence of the electrochemic al recycling of substrate which occurs upon transduction.