DETERMINATION OF VICINAL DIKETONES IN BEER BY GAS-CHROMATOGRAPHY (HEADSPACE TECHNIQUE) - COLLABORATIVE TRIAL

Two methods for the determination of vicinal diketones in beer have be en collaboratively tested by the Analysis Committee of the Institute o f Brewing and are recommended for use. Both methods employ gas chromat ography and are essentially the same, except that one relies on the us e of a packed column and the other on a capillary column. For diacetyl it was judged that repeatability (r95) values were independent of con centration over the range 0.04 to 0.19 mg/litre. Over this range, r95 values for diacetyl of 0.028, 0.020 and 0.026 mg/litre were obtained f or capillary, packed columns and combined results respectively. Values for reproducibility (R95) were judged to be dependent on the mean lev el (m). R95 values were 0.032 + 0.68 m, 0.01 + 0.47 m and 0.005 + 0.67 m were obtained for capillary, packed columns and combined results re spectively. For both methods the r95 and R95 values for 2,3-pentanedio ne were judged to be independent of concentration over the range 0.02 to 0.07 mg/litre. For capillary columns, packed columns and combined r esults respectively, r95, values were 0.009, 0.009, 0.010 mg/litre and R95 values were 0.037, 0.042 and 0.038 mg/litre.