Mass spectrometry of N-nitrosamines

The preparation of a series of N-nitrosamines for carcinogenicity studies presented an opportunity to study mass spectral fragmentation schemes in detail. Condensed spectra are listed for 146 N-nitrosamines of widely differing structures, including nitroso derivatives of commercial drugs and insecticides. Aliphatic nitrosamines were generally characterized by molecular ions and loss of OH. Subsequent fragmentation via alpha-cleavage is similar to that of aliphatic amines. The loss of OH is believed to result in a cyclic ion. Subsituted aliphatic nitrosamines varied in fragmentation schemes with structure and position of the substitutent groups. However, most showed alpha-cleavage at some point in fragmentation. When substituted with aromatic groups prominent peaks due to the aromatic moiety were observed. The alicyclic nitrosamines showed losses of NO, NOH and OH and subsequent alpha-cleavages. Nitrosamides were characterized by rupture of the carbonyl to nitrogen bond. Spectra of substituted ureas usually showed charge retention by the carbonyl fragment, while carbamate esters showed ions from both fragments.