Bi-enzyme reactor for electrochemical detection of low concentrations of uric acid and glucose

Abstract

An enzyme-based flow-injection amperometric analysis system (FIA) for monitoring of uric acid and glucose is described. The oxidase and peroxidase enzymes are physically coimmobilised in a sandwich-type reactor and ferrocene serves as a mediator. The assays are based on the measurement of a reduction current resulting from the enzymatic reactions, at a glassy carbon electrode held at 0.00 mV (vs. Ag/AgCl). The high selectivity (ascorbic acid did not interfere) is coupled to high sensitivity (a detection limit of 30 and 60 nmol/l for uric acid and glucose, respectively; signal/noise = 3) and good stability (the enzymes remained active for more than 6 weeks at 30(C). The usefulness of the assay in clinical chemistry is illustrated by the measurement of human serum uric acid and glucose concentration. The results obtained were in fairly good agreement with those obtained using conventional hospital laboratory methods.