Peroxidase- and tetracyanoquinodimethane-modified graphite paste electrode for the measurement of glucose/lactate/glutamate using enzyme-packed bed reactor.

A flow injection analysis sensor for the measurement of glucose/lactate/glutamate is reported. The glucose oxidase/glutamate oxidase/lactate oxidase was immobilized on silanized controlled pore glass particles and packed into a Teflon column (i.d., 1.2 mm; length, 40 mm) to give a bed for glucose/lactate/glutamate. The hydrogen peroxide formed by the enzymatic reaction in the packed bed was monitored by a horseradish peroxidase- and tetracyanoquinodimethane (TCNQ)- modified graphite paste electrode at 50 mV vs Ag/AgCl. The glucose oxidase/lactate oxidase/glutamate oxidase were regenerated in the packed bed, whereas peroxidase was regenerated in the TCNQ-mediated graphite paste electrode by the oxidation of TCNQ. The oxidized TCNQ was electrochemically reduced at 50 mV vs Ag/AgCl. The cathodic current obtained by the reduction of TCNQ determined the concentration of the injected analytes in the packed bed. The system showed very rapid response. Response curves for the analysis of peroxide, glucose, lactate, and glutamate are reported.