AMPEROMETRIC GLUCOSE SENSOR BASED ON GLUCOSE-DEHYDROGENASE IMMOBILIZED ON A GRAPHITE ELECTRODE MODIFIED WITH AN N, N'-BIS(BENZOPHENOXAZINYL) DERIVATIVE OF BENZENE-1,4-DICARBOXAMIDE

A bis(benzophenoxazinyl) derivative of benzene-1,4-dicarboxamide (BPT) was synthesized by coupling Nile Blue with terephthaloyl chloride. The BPT adsorbed on a graphite rod electrode catalysed the electrochemical oxidation of 1,4-dihydronicotinamide adenine dinucleotide (NADH) at potentials more positive than -200 mV vs. Ag/AgCl at pH 7.0. When using BPT-modified electrodes as the amperometric sensors in a single-channel flow-injection system, rectilinear calibration graphs were obtained in the range 0.3-mu-M-2 mM NADH for 50-mu-l samples injected. No decrease in the response to NADH was observed for at least 2 weeks of continuous daily operation of the sensor at pH 5-9. An amperometric glucose sensor was prepared by cross-linking glucose dehydrogenase with glutaraldehyde on the surface of a BPT-modified electrode. Its response to glucose and to NADH remained constant for 30 days of daily flow-injection experiments at pH 6.5. The calibration graphs were rectilinear for 3-500-mu-M glucose. A sample throughput of 200 h-1 was attained.