GLUCOSE-OXIDASE ENZYME ELECTRODE - RELATION BETWEEN INNER MEMBRANE-PERMEABILITY AND SUBSTRATE RESPONSE

Permeability coefficients, P (cm2 s-1), for H2O2 and O2 across micropo rous polycarbonate membranes of varying pore radii together with simil ar 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 a s inner membranes of glucose oxidase electrodes. Organosilane coated p olycarbonate membranes were found to impart extended linearity ranges (> 40 mM) to glucose enzyme electrodes. The O2/glucose permeability co efficient (P) ratio of such inner membranes was found to be critical i n determining sensor performance. It is proposed that for the oxidase based electrodes used, extensions in linearity were due to the cumulat ive effect of two phenomena. Firstly the relative augmentation of O2 r eturning into the enzyme layer following the oxidation of H2O2 helps f ree the sensor from the effects of low ambient pO2 levels. Secondly in ner membrane barriers offering increased diffusional resistances towar ds H2O2 maintain linear diffusion of H2O2 to the working electrode at higher substrate concentrations.