Amperometric determination of ethanol in beverages at copper electrodes in alkaline medium

Abstract

Abstract The anodic oxidation of ethanol at copper surfaces in alkaline medium has been reported. The participation of electrogenerated Cu(III) species in the electrocatalysis of the oxidation of ethanol at copper surfaces was investigated by rotating ring-disc voltammetry and a mechanism involving the participation of radicals was proposed. The copper oxide sensor was assembled in a wall-jet electrochemical cell and a FIA method that incorporates flow extraction of ethanol through a PTFE membrane at room temperature was developed. Under optimal experimental conditions the peak current response (measured at 0.5 V versus Ag/AgCl) increases linearly with ethanol concentration over the range 2–10% (v/v). The repeatability of the electrode response in the FIA configuration was evaluated as 3% ( n =20) and the limit of detection of the method was 0.4% ( S / N =3). The analytical frequency was estimated to be 120 h −1 . Experiments to investigate the selective of the PTFE membrane were carried out and they demonstrated that only small molecules such as methanol may interfere in the determination of ethanol. For some samples of different alcoholic beverages, the results showed excellent agreement ( r =0.998) with the ones obtained by using gas chromatography.