Confirmation of N-nitrosodimethylamine and N-nitrosopyrrolidine in foods by conversion to their nitramines with pentafluoroperoxybenzoic acid.

A method is presented, wherein concentrated dichloromethane extracts from malt, beer, and nonfat dried milk powder containing N-nitrosodimethylamine (NDMA), and fried dry-cured and pump-cured bacon containing NDMA and N-nitrosopyrrolidine (NPYR) undergo 3N HClO4-Celite microcolumn cleanup followed by peroxidation with pentafluoroperoxybenzoic acid, a stable solid peroxyacid, to N-nitrodimethylamine and N-nitropyrrolidine, as an aid to nitrosamine confirmation. The nitramine-containing solution underwent further cleanup with 6N HClO4-Celite and acid alumina-6% H2O microcolumns for subsequent analysis by gas chromatography interfaced with thermal energy analyzer and 63Ni electron capture detectors. With a 20 g sample, 1 ppb NDMA and 2.5 ppb NPYR could be confirmed by this method. The extract can be concentrated further before analysis, so the detection level can be reduced to less than 1 ppb NDMA and 1 ppb NPYR.