LOW-POTENTIAL STABLE DETECTION OF BETA-NADH AT SOL-GEL DERIVED CARBONCOMPOSITE ELECTRODES

Sol-gel derived carbon composite electrodes, prepared from different n on-silicate metal alkoxide precursors, offer a substantial decrease in the overvoltage of the NADH oxidation reaction (compared to ordinary carbon electrodes). Such promotion is attributed to acceleration of th e proton-transfer step by the metal-oxide component of the composite. Passivation problems, accrued by accumulation of reaction products, ar e also greatly minimized. Both titania-, zirconia-sol-gel carbon compo site electrodes thus offer a highly sensitive and stable anodic detect ion of NADH at +0.2 V. Greatly improved retention of the redox mediato r Meldola Blue within the sol-gel network permits convenient measureme nts at NADH at -0.1 V. These improvements indicate great promise for t he design of dehydrogenase-based amperometic biosensors. An intrinsic activation action by the metal-oxide component is also reported toward s the oxidation of hydrazine, hydrogen peroxide, ascorbic acid and cat echol. Low-potential detection of NADH is also illustrated at microfab ricated titania/carbon screen-printed electrodes. (C) 1998 Elsevier Sc ience B.V.