Potentiometric Determination of Ethanol in Alcoholic Beverages Using a Flow-Injection Analysis System Equipped with a Gas Diffusion Unit with a Microporous Poly(tetrafluoroethylene) Membrane

Abstract

The selective determination of ethanol in alcoholic beverages is performed by a flow-injection analysis method using gas-diffusion separation. The determination is based on the oxidation of alcohol permeating across a porous membrane with dichromate and the reduction of excess dichromate with ferrous ion in a flow system. The concentration of ferric ion formed is potentiometrically measured with an oxidation-reduction potential electrode and is indirectly related to the alcohol content of the sample. Analytical results using the proposed method are in agreement with those obtained by a specific-gravity method (current official method in Japan) as well as by a gaschromatographic determination.