Determination of N-nitrosodimethylamine by HPLC, with fluorescence detection.: A survey of N-nitrosodimethylamine in commercial beers

A new method has been developed for determination of N-nitrosodimethylamine (NDMA) in beers. Beer samples, previously degassed, were extracted with diethyl ether containing 25% 2-propanol and the extract was denitrosated by hydrobromic acid-acetic acid to produce secondary amines. These amines were then subjected to microwave-assisted reaction with dansyl chloride to form dansyl derivatives in 5 min, using radiation power of 378 W and a maximum pressure of 1.4 bar inside the reactor. The reaction mixture was analyzed by HPLC on a C-18 column with acetonitrile-water (55/45, v/v) as mobile phase with fluorimetric detection at 53 1 mu (excitation at 339 nm). The detection limit of method is 0.04 mug/L. N-nitrosodimethylamine was found in 20% of the beer samples at levels ranging from 0.04 to 0.50 mug/L. The mean NDMA level for whole beers (44 samples) was 0.16 +/- 0.25 mug/L with a range from ND to 1.05 mug/L.