A tandem mass spectrometry investigation of the gas phase chemistry of N-nitrosamines
This thesis is an investigation of the gas phase chemistry of seven N-nitrosamine compounds. N-nitrosodimethylamine (NDMA) and its deuterated analogue (NDMA-d6), N-nitrosodi-n-propylamine (NDPA) and its deuterated analogue (NDPA-d14), N-nitrosomorpholine (NMOR), N-nitrosopiperidine (NPIP), and N-nitrosopyrrolidine (NPYR) were subjected to collision-induced dissociation using electrospray ionization - tandem mass spectrometry, in an ion trap instrument. Detailed dissociation mechanisms were proposed for each ofthe seven N-nitrosamines. For NDMA, NDMA-d6 and NMOR, a radical cleavage initiated the formation of major products. For NDPA, NDPA-d14, NPIP, and NPYR, electrocyclic processes gave rise to the highest intensity spectral peaks. These fundamental differences in dissociation were related to the structure of the N-nitrosamines. In the case of NMOR, its dissociation differed from the other cyclic compounds due to the presence of an electronegative heteroatom within the ring structure. In the case of NDMA and NDMA-d6, it was the short chain length of of the methyl substituent groups which was believed to cause the radical-type cleavages. The dissociation products of the N-nitrosamines studied were related to their carcinogenic properties upon metabolic activation. Novel reactions of gas-phase ions with neutral water and methanol molecules, in the ion trap, were described, These illustrate the highly reactive nature of alkylating species generated by N-nitrosamines, and help correlate gas-phase ion trap studies, with the process which occurs in the biological metabolism of N-nitrosamines. The detailed tandem mass spectral data presented can also be useful for the environmental analysis of N-nitrosamines.