ABSTRACT
An electrical equivalent circuit model of an enzyme electrode is presented. Measurements made using Nafion-immobilised urease electrodes were found to correlate well with the theoretical model. Modelling of the experimental data has elucidated the changes that take place in all constituent phases during the sensor detection process. The results are consistent with the ability of Nafion to bind positive ammonium ions produced by enzyme action, which produces a decrease in electrode polarisation. As a consequence of this, Nafion-immobilised electrodes are well suited to measurements at physiological electrolyte concentrations. Measurements in sheep serum are included.
