Determination of o-isobutyl-s-[(2-diethylamino)ethyl]-methyl phosphonothioate and the hydrolysis toxic product traces by liquid chromatography-tandem mass-spectrometry

Abstract

To date, chemical weapons in the Russian Federation have been completely destroyed. Former chemical weapons destruction facilities (CWDFs) are subject to re-profiling. The most important stage of this activity is to assess the safety of engineering elements of the facilities to find out whether they can be involved in national economy. The most toxic and persistent substance processed at the CWDFs was a V-series agent. The certified gas chromatographic methods previously used for control of residual amounts of this substance on the surfaces and in deep layers of materials were based on its conversion to acid fluoride on silver fluoride pads. The latter are no longer produced, and these methods are impossible to use. The use of liquid tandem chromatography-mass spectrometry (HPLC-MS/MS) provided a direct determination of VR in the different matrices at the level of the toxicity threshold. At the same time HPLC-MS/MS method allows to determine the toxic acid formed by the hydrolysis of the P–O bond in the VR molecule. Previously no methods for the determination of this acid were available. A unified procedure for the sensitive target determination of VR (O-isobutyl S- (2-diethylamino)ethyl methylphosphonothioate) and its most toxic hydrolysis product S-[(2-diethylamino)ethyl] methylphosphonothioic acid in surface wipes and in deep layers of various materials is proposed. The method involves the addition of an internal standard (paraoxon) to the sample, extraction with methanol, concentration of the extract, and analysis by HPLC-MS/MS in the multiple reaction monitoring (MRM) mode. The detection limits of the analytes are close to their toxic threshold levels. Special emphasis in the procedure is paid to the reliability of identification of the analytes, which is of key importance in international investigations under the Chemical Weapons Convention.