Gas chromatography-mass spectrometric analysis of trimethylsilyl derivatives of toxic hydrolyzed products of nerve agent VX and its analogues for verification of Chemical Weapons Convention

Abstract

The formation of trimethylsilyl (TMS) derivative of hydrolyzed product of nerve agent VX, namely S-2-(N,N-diisopropylaminoethyl) methylphosphonothiolate (EA-2192), was reported to be hampered due to its zwiterionic character. Contrary to this assumption, we have synthesized and analyzed the TMS derivative of EA-2192 and its analogues. Initially, the problem of non-detectability in GC-MS analysis was found to be due to their condensation followed by decomposition on GC column. An optimized temperature program, starting from 175 °C column temperature, favours partitioning of TMS derivatives of EA-2192 and its analogues into mobile phase, which facilitates their detection. It reduces their on-column condensation and decomposition. Excellent reproducibility (<1% RSD) of TMS derivatives of S-2-(N,N-dialkylaminoethyl) alkylphosphonothiolates was achieved by GC-MS analysis with temperature program of 175 °C (2 min)–10 °C min⁻¹– 300 °C (5 min). Under the optimized conditions LODs ranged from 8–10 μg mL⁻¹ for different analytes at a split ratio of 1 : 10.