Software-Assisted Automated Detection and Identification of "Unknown" Analogues: Implementation on V-Type Nerve Agents.

ABSTRACT

V-type nerve agents are among the most toxic organophosphorus chemical warfare agents, and they are under strict regulation and supervision by the OPCW (Organization for the Prohibition of Chemical Weapons). The V-type class of materials refers to a potentially large number of analogues and isomers. In order to expose instances of unfulfillment of the OPCW treaty, it is essential to have the ability to detect and identify "unknown" analogues of this family, even in the absence of an analytical standard. This work demonstrates a new automated tool for the detection and identification of V-type analogues, using high-resolution-accurate-mass LC-MS analysis, followed by "Compound Discoverer" software data processing. This software, originally developed for metabolism and metabolomics screening, is used here to automatically detect various V-type analogues by picking peaks and comparing them to "in-silico" calculated modifications made on a predefined basic V-backbone structure (according to the OPCW definitions for V-type agents). Subsequently, a complete structural elucidation for the proposed molecular formula is obtained by MS/MS data analysis of the suspected component, for both the V-type analogue (using ESI(+) analysis) as well as its hydrolysis product (using ESI(-) analysis) for a better elucidation of the phosphonate "head" structure. This method was found to be useful for the detection and identification of several "unknown" analogues, at low ng/mL levels in soil extracts.