ELECTROCATALYTIC OXIDATION OF ASCORBIC-ACID AT CHEMICALLY MODIFIED ELECTRODES

Electrocatalytic oxidation of ascorbic acid (AA) in aqueous buffer solutions at the p-tetracyanoquinodimethane (TCNQ)-, ferrocene (Fc)-, 1,1'-dimethylferrocence (DMFc)-, and tetrathiafulvalene (TTF)-modified graphite electrodes is carried out at each modifier's redox potentials. Over the linear range of current dependence on AA concentration, the sensitivity of the electrocatalytic systems corresponds to up to 0.1 A/M. At pH 6.5-8.0 a change in the electrocatalytic process rate is less evident (for TCNQ, TTF) or is increased by a factor of 4.9 (DMFc). The electrocatalytic current is only slightly dependent on electrode rotation speed. The electrodes retain about 80% of their initial response over a 2-month period of operation.