DETERMINATION OF N-NITROSODIMETHYLAMINE IN BEER BY GAS CHROMATOGRAPHY-STABLE ISOTOPE-DILUTION CHEMICAL-IONIZATION MASS-SPECTROMETRY

A sensitive method for the determination of N-nitrosodimethylamine in beer samples is described. The analyte was isolated by distillation an d subsequent extraction from the distillate using dichloromethane. Ana lysis was carried out by gas chromatography combined with positive-ion chemical ionization mass spectrometry. Quantification was performed b y stable isotope dilution using [H-2(6)]-N-nitrosodimethylamine as the internal standard. The measurements exhibited excellent linearity in the range 0.10-4.00 mu g kg(-1) (r = 0.99999) and a detection limit of 0.04 mu g kg(-1) was achieved. The between-sample relative standard d eviation of the method was 0.73% (n = 5) at a concentration level of 0 .86 mu g kg(-1) The recovery of the compound was 78 +/- 2.1%. The prop osed procedure seems to be a good alternative to the frequently used g as chromatography-thermal energy analysis approach for the determinati on of N-nitrosodimethylamine.