AC impedance analysis of enzyme-functional electrodes

AC impedance spectra were measured for mediated bioelectrocatalytic systems containing PQQ-dependant glucose dehydrogenase, ferrocenecarboxylic acid and D-glucose. The catalytic system showed a circular arc in Nyquist plots, and its radius was inversely proportional to the mediator concentration. The kinetic parameters were evaluated with theoretical equations for the case in which the substrate concentration was sufficiently higher than the Michaelis constant, and the mediator concentration was sufficiently lower. The evaluated value of the kinetic parameter was comparable to that obtained by cyclic voltammetry, indicating the usefulness of AC impedance methods for bioelectrocatalysis systems.