FLOW-INJECTION AMPEROMETRIC DETERMINATION OF GLUCOSE AND SOME OTHER LOW-MOLECULAR-WEIGHT SACCHARIDES BASED ON OLIGOSACCHARIDE DEHYDROGENASEMEDIATED BY BENZOQUINONE SYSTEMS

A comparison has been made on the performance of different oligosaccha ride dehydrogenase (ODH) modified electrodes as sensors for the detect ion of a series of mono-, di-, and oligosaccharides. Monomeric benzoqu inone (BQ) or poly(ether amine benzoquinone), PEAQ, as electron transf er mediators were used for the preparation of the electrodes. Four sen sor configurations operating in the flow injection mode were studied: (i) ODH adsorbed on the surface of solid graphite with BQ in the now c arrier solution; (ii) ODH doped into the bulk of carbon paste electrod e with BQ in the now carrier solution; (iii) ODH and BQ doped into the bulk of carbon paste electrode, and (iv) ODH and PEAQ doped into the bulk of carbon paste electrode. All four systems responded to glucose and equal responses were obtained for the alpha- and the beta-anomeric forms. The best sensitivity for glucose was obtained with the solid O DH-modified electrode, which was equal to 1.8 mu A mM(-1) cm(-2). The lowest noise was inherent for carbon paste electrodes with BQ in the p aste. For this electrode configuration the responses for 16 sugars wer e observed. The highest currents were obtained for glucose (100%), lac tose (52%), cellobiose (50%), and maltose (49%). For all four sensor s ystems selectivity profiles were almost the same.