Affiliation: Department of Chemistry,” Sapienza” University of Rome, p.le A. Moro 5, 00185 Rome, Italy.
Two different enzyme electrodes for the determination of ethanol in alcoholic beverages were developed by immobilizing alcohol oxidase or catalase in a k-Carrageenan gel layer overlapping an amperometric gaseous diffusion Clark type oxygen electrode. The response of biosensors toward standard solutions of ethanol,methanol, n-propanol, n-butanol, ethylenglycol and glycerol was recorded, compared and discussed. In the characterization studies of the biosensors several parameters such as pH, operational stability, response time, analysis time and calibration repeatability, between-days and between-electrodes, calibration reproducibility, linearity, and sensitivity, were studied. Finally by using the developed biosensors, the ethanol concentration of several commercial wine and beer samples was determined. The results, obtained with the two enzyme electrodes, were compared and the correlation evaluated by statistic tests. The biosensor method using catalase enzyme seemed to be the most suitable of the two enzyme devices for a selective and less expensive determination of ethanol in alcoholic beverages. The catalase enzyme electrode actually showed the greatest selectivity to ethanol, of all the alcohols tested. The response of the catalase biosensor was not influenced by the presence of the methanol in particular and its operational stability was found to be significantly higher than that of the alcohol oxidase sensor. The only drawback associated with the use of the catalase biosensor, compared to the method based on alcohol oxidase, is the slightly increased time required to perform the ethanol analysis in each sample of alcoholic beverage.