ELECTROCHEMICAL OXIDATION OF H2O2 ON PT AND PT + IR ELECTRODES IN PHYSIOLOGICAL BUFFER AND ITS APPLICABILITY TO H2O2-BASED BIOSENSORS

The electrochemical oxidation of hydrogen peroxide on Pt disk and Pt + Ir wire electrodes was studied in physiological buffer at pH 7.40 in order to establish a practical protocol for H2O2-based biosensors. The electrode reaction is a two-electron irreversible process. The oxidation of H2O2 on Pt and Pt + Ir electrode surfaces is a catalytic reaction which is H2O2 concentration dependent but O2 pressure independent at low H2O2 concentration. Amperometric detection of H2O2 is strongly affected by pH, temperature and electrode surface conditioning. An oxidized surface is required to obtain a stable H2O2 response, and reductive pretreatment of the electrode always yields prolonged stabilization times. The application of a cellulose acetate membrane to the surface can protect the oxidized sur-face and therefore substantially reduce the stabilization time for H2O2 measurements.