ELECTRON-TRANSFER RATES IN ELECTROACTIVE FILMS FROM NORMAL PULSE VOLTAMMETRY - MYOGLOBIN SURFACTANT FILMS

A diffusion-kinetic model for normal pulse voltammetry was evaluated for the estimation of standard heterogeneous rate constants (k-degrees') and charge transport diffusion coefficients (D') for films on electrodes featuring small signal to background ratios. Individual voltammograms are easily tested for adherence to the model. Analysis of errors by using nonlinear regression of theoretical data indicated that reliable determination of electron transfer rate constants requires use of an optimum pulse width range, depending mainly on kappa = k-degrees'/D1/2. The method was applied to 20-mum-thick, liquid crystal films of didodecyldimethylammonium bromide containing the heme protein myoglobin. Values of k-degrees' and D' were in good agreement with those obtained by cyclic voltammetry. Pulse widths of less-than-or-equal-to 10 ms were required for reliable k-degrees' values, while longer pulse widths gave reliable D' values.