RAPID-DETERMINATION OF ETHANOL IN FOOD BY COMBINATION OF QUINONE-DEPENDENT ALCOHOL-DEHYDROGENASE REACTION AND SELF-DRIVEN COULOMETRY

A new method for determination of ethanol was developed by combining a quinone-dependent alcohol dehydrogenase reaction and self-driven coul ometry and applied for determination of ethanol in food. Enzyme reacti on was carried out in a mixture consisting of MacIlvaine buffer (pH 5. 0), ubiquinone-0 (Q(0)), guinone-dependent alcohol dehydrogenase and a sample. An aliquot of the reaction mixture was then added to the self -driven coulometric cell to determine the amount of reduced Q(0) by co ulometry. In a range of 0.1 to 30% (v/v) of ethanol, the measured tota l charge was almost the same of the theoretical and correlated with th e ethanol concentration with a correlation coefficient of 0.9997, sugg esting that ethanol was measured without calibration. Ethanol concentr ation in twenty daily foods determined by this method were correlated with those determined by gas chromatography with correlation coefficie nt of 0.9991 and coefficient of Variation of ten trials was below 2%. The measuring time in the self-driven coulometry was 1 to 5 min. After 100 trials of addition of a sample on the carbon-felt electrode in th e self-driven coulometric cell, no effect on the These results indicat ed that ethanol in food was rapidly determined by total charge was obs erved. this new method.