Studies of Electrocatalytic Reactions of NADH at Mediator Modified Electrodes and of H2O2 at Peroxidase Modified Electrodes

Abstract: This thesis addresses: (1) studies of direct and mediated electron transfer and kinetics of peroxidases on electrodes and the development of amperometric peroxidase-based biosenors, (2) electrochemical and kinetic studies of NADH oxidation at mediator modified electrodes. The direct and mediated electron transfer of horseradish and tobacco peroxidase were investigated on graphite electrodes by using wall-jet electrode methodology. Biosensors based on novel plant peroxidases for determination of phenolic compounds were developed. The electrochemical properties of different redox mediators immobilised on titanium phosphate, zirconium phosphate or silica gel were studied by means of cyclic voltammetry. The mediator properties for electrocatalytic oxidation of 1,4-dihydronicotinamide adenine dinucleotide (NADH) at the chemically modified electrodes are presented. For the kinetic investigations the rotating disk electrode methodology was used. The interaction between some of the mediators and titanium phosphate was investigated by means of attenuated reflectance infrared spectroscopy and the possible leakage of the mediators from the electrode was investigated by using fast scan cyclic voltammetry and scanning electrochemical microscopy.