Chemically immobilised bi-enzyme electrodes in the redox mediated mode for the flow injection analysis of glucose and hypoxanthine

Abstract

Flow injection analysis systems incorporating amperometric bi-enzyme electrodes for glucose and hypoxanthine determination are described. The sensors were based on glucose oxidase-peroxidase for the determination of glucose and xanthine oxidase-peroxidase for the determination of xanthine and hypoxanthine and the enzymes were immobilised on nylon mesh and held over a platinum electrode. The hydrogen peroxide product of the enzymatic catalysis was monitored amperometrically in a three-electrode Stelte cell, adapted for flow injection analysis, after its peroxidase-catalysed reaction with hexacyanoferrate(II).

The use of the hexacyanoferrate(II) mediator permitted a low applied potential (–100 mV vs. Ag-AgCl) to be used, enabling the determination of glucose in blood serum samples without difficult sample pre-treatment. The xanthine oxidase-peroxidase bi-enzyme electrode was used to determine hypoxanthine in fish meat as an indicator of deterioration during storage and the results compared favourably with an alternative spectrophotometric approach recommended by the Analytical Methods Committee (AMC) according to the equation [hypoxanthine]_Electrode= 1.01[hypoxanthine]_AMC+ 4.0 × 10^–3, with a correlation coefficient of 0.998.