Quantification of nerve agent adducts with albumin in rat plasma using liquid chromatography–isotope dilution tandem mass spectrometry

A sensitive method for the determination of the organophosphorus nerve agents sarin, soman and VX adducts with tyrosine residue of albumin in rat plasma has been developed and validated using liquid chromatography–isotope dilution tandem mass spectrometry (LC–IDMS/MS). O-(O-Alkyl methylphosphonyl) tyrosine adducts and their deuterated products that were used as the internal standards were synthesised to establish the quantitative isotope-dilution method. Protein purification and solid-phase extraction (SPE) were applied to improve the recovery efficiency, reduce interference and achieve high sensitivity. The method provided a detection limit of 0.01 ng/mL for sarin and soman adducts and 0.05 ng/mL for the VX adduct. The value of the intra-day relative standard deviation over the calibration range was less than 6.16% (n = 6), and that of the inter-day was less than 12.7% (n = 6). The recovery varied from 86% to 111%. This sensitive method was successfully applied to the analysis of adducts in rat plasma after nerve agent exposure, and the results demonstrated the dose–effect relationships.