Glucose oxidase enzyme electrode: relation between inner membrane permeability and substrate response

Abstract

Permeability coefficients, P (cm 2 s −1), for H 2O 2 across microporous polycarbonate membranes of varying pore radii together with similar membranes coated with an organosilane have been determined, using a classical diffusion chamber. A correlation has been attempted between the permeability of such membranes with their performance when used as inner membranes of glucose oxidase electrodes. Organosilane coated polycarbonate membranes were found to impart extended linearity ranges ( > 40 mM) to glucose enzyme electrodes. The O 2/glucose permeability coefficient ( P) ratio of such inner membranes was found to be critical in determining sensor performance. It is proposed that for the oxidase based electrodes used, extensions in linearity were due to the cumulative effect of two phenomena. Firstly the relative augmentation of O 2 returning into the enzyme layer following the oxidation of H 2O 2 helps free the sensor from the effects of low ambient pO 2 levels. Secondly inner membrane barriers offering increased diffusional resistances towards H 2O 2 maintain linear diffusion of H 2O 2 to the working electrode at higher substrate concentrations.