DETERMINATION OF DIACETYL IN BEER USING DIFFERENTIAL-PULSE POLAROGRAPHY

A Polarographie method is proposed for the determination of diacetyl and other vicinal diketones in beer. Similar to the EBC official spectrophotometric method, diacetyl is derivatised with o-phenylene-diamine, producing 2,3-dlmethylquinoxaline, a polarographically active compound. The Polarographic method allows discrimination between diacetyl and methylglyoxal and a detection limit ten times lower than the EBC method is obtained. In addition, problems of erratic results for diacetyl may be avoided and data are in good agreement with those obtained by gas chromatography with electron capture detection and headspace sampling. It is suggested that high results obtained with the spectrophotometric method may be attributed to an erroneous procedure used in the spectrophotometric calculations. An alternative procedure is proposed, with which lower values for diacetyl in beer are obtained, similar to those found with other methods. These low diacetyl values are near the detection limit of the spectrophotometric method.