Microseparation chips for performing multienzymatic dehydrogenase/oxidase assays: Simultaneous electrochemical measurement of ethanol and glucose

This report describes a new "lab-on-a-chip" protocol integrating on-line pr ecolumn biocatalytic reactions of multiple (oxidase and dehydrogenase) enzy mes and substrates with effective capillary electrophoresis microseparation s and amperometric detection. The operation of the new oxidase/dehydrogenas e reaction/separation microchip is illustrated for the simultaneous measure ment of glucose and ethanol in connection to the corresponding glucose oxid ase and alcohol dehydrogenase reactions, respectively. The enzymatic reacti ons generate hydrogen peroxide and NADH species that are separated ton the basis of their different charges) and detected amperometrically at the end- column thick-film detector. A driving voltage of 2000 V results in peroxide and NADH migration times of 74 and 230 s, respectively. Operating the gold -coated carbon detector at +1.0 V allows simultaneous anodic detection of b oth reaction products. Factors influencing the reaction, separation,, and d etection processes are examined and optimized. The applicability of the new multienzyme assay to wine samples is illustrated.