Analysis of degradation products of organophosphorus chemical warfare agents and related compounds by liquid chromatography–mass spectrometry using electrospray and atmospheric pressure chemical ionisation

Abstract

A qualitative screening procedure was developed for the detection and identification of phosphonic acid hydrolysis products of organophosphorus chemical warfare agents, using liquid chromatography–mass spectrometry with electrospray ionisation (LC–ESP-MS). A mixed C8/C18 reversed-phase column with gradient elution gave good chromatography for a series of phosphonic acids. Detection limits for aqueous solutions of standards were <50 ng/ml (<0.25 ng injected), providing an increase in sensitivity up to an order of magnitude compared with LC–MS using atmospheric pressure chemical ionisation (LC–APCI-MS). The methodology provides a rapid screening procedure for the hydrolysis products of nerve agents in aqueous samples and extracts. The application of LC–ESP/APCI-MS and LC–ESP/APCI-MS–MS to the identification of dialkyl esters of phosphonic acids is also described. Examples are given of the application of LC–MS to spiked water samples analysed during the course of proficiency testing.