Automatic multicommutated flow system for ethanol determination in alcoholic beverages by spectrophotometry

In this work, we describe a automatic spectrophotometric procedure for ethanol determination in alcoholic beverages by employing a flow system based on a multicommutation and binary sampling approach. The method was based on ethanol oxidation by dichromate in sulfuric acid medium and detection by spectrophotometry. The procedure was applied to ethanol determination in sugar-cane spirit, whisky, and brandy. Accuracy was assessed by comparing the results with those obtained by densimetry for sugar-cane-spirit samples and by the standard-addition technique for whisky and brandy samples. In the first case, no significant difference at the 95% confidence level was observed and in the second case, recovery ranging from 95 to 109% was achieved. Other profitable features such as an analytical throughput of 40 determinations per hour, a relative standard deviation of 1.6% (n = 11) for a typical sample presenting 42.1% (v/v) ethanol, and a reagent consumption of 5.4 mg K₂Cr₂O₇ per determination generating a low volume of waste per determination (3.3 mL) were also achieved. © 2000 John Wiley & Sons, Inc. Lab Robotics and Automation 12:31–36, 2000