Confirmatory method for N-nitrosodimethylamine and N-nitrosopyrrolidine in food by multiple ion analysis with gas chromatography-low resolution mass spectrometry before and after ultraviolet photolysis.

A confirmatory procedure is described for determining N-nitrosodimethylamine (NDMA) and N-nitrosopyrrolidine (NPYR) in bacon, beer, and malt by gas chromatography-low resolution quadrupole mass spectrometry (GC-MS). The presence of 3 monitored ions, m/z 30, 42, and 74 for NDMA, and m/z 30, 42, and 100 for NPYR, before and disappearance after photolysis under UV light at 365 nm without quantitation of peak areas was considered confirmatory evidence for their presence. The extracts, obtained by mineral oil distillation methods for bacon and malt, and dry column methods for bacon and beer, underwent cleanup procedures before capillary GC-MS analysis. Less than 100 ng nitrosamine in the total extract, or approximately 2 ng NDMA or 3 ng NPYR injected into the GC-MS instrument, can be confirmed by this method. This technique should also be applicable for other volatile nitrosamines.