Fragmentation mechanisms in mass spectrometry of organophosphorus compounds: implications for analysis in chemical weapons convention framework

Abstract

Detection and identification of chemical warfare agents and their precursors/reaction products in various environmental matrices are important tasks which are considered in chemical weapons convention (CWC). 2-[(2-chloroethyl)(alkyl)amino]ethyl alkyl methylphosphonates I and N-alkyl bis(2-(alkoxy-methylphosphoryloxy)amines II are covered under schedule 2.B.4 of CWC and have structures closely related to the nerve and blister agents. In fact, they are products of the reactions between these two different CWC scheduled compounds: nerve agents and nitrogen mustards. Ion fragmentations during mass spectrometry studies of these chemicals were investigated using electron ionization mass spectrometry. Structures of fragments were confirmed using EI-MS analysis of the deuterated analogs. Density functional theory was also used to show preferred fragmentation pathways. Mass spectrometric studies revealed some fragmentation pathways, such as, McLafferty-type and hydrogen rearrangements and elimination of chlorine, chloromethylene radical, alkene and HCl.