Determination of free G-type nerve agents in blood: in situ derivatization on a dried blood spot (DBS) paper followed by LC–MS/MS analysis

Abstract

G-type nerve agents, including sarin, soman and cyclosarin are potent neurotoxic chemical weapons, sarin of which is the most used chemical warfare agent of our time. These compounds have limited stability, are highly reactive in the body and thus require the detection of stable metabolites, mainly their hydrolysis products or adducts to proteins. The aim of this study was to develop a new method for the determination of trace amounts of intact G-type nerve agents from small amounts of whole blood. The G-agents were derivatized on a dried blood spot (DBS) paper with 2-((dimethylamino)methyl)phenol. After drying, they were extracted from the paper and analyzed by liquid chromatography–tandem mass spectrometry (LC–MS/MS) or Orbitrap LC–MS/MS. Recoveries of ~ 34% were obtained in the range of 3–300 ng/mL with good linear response. A detection limit as low as 0.7 ng/mL in whole blood was demonstrated. Derivatized sarin was stable on the DBS paper for 19 days at room temperature before analysis. The method was applied for the short-time-course determination of free sarin in mouse blood after in vivo intranasal exposure to 3LD50 sarin. A fast-time-course decay (t1/2: ~ 2 min) was observed, with blood sarin concentrations in the range of 6−60 ng/mL in the post-exposure time range of 1−7 min. This method is simple and unique, enabling the monitoring of G-agents before their rapid conversion in the body. The technique can serve for the study of very fast decay mechanisms of drugs and toxic materials in the body.