A Method for the Analysis of Tabun in Multisol Using Gas Chromatographic Flame Photometric Detection

Preparation and analysis of tabun (GA) solutions are necessary for the continued development of countermeasures to this nerve agent. GA solutions must be stable and compatible for use in the test systems chosen for study; however, GA is very unstable in saline solutions. In the past we have found GA in saline at 2 mg/mL to be stable for a month or less at −70°C, whereas saline solutions of sarin (GB), soman (GD), and cyclosarin (GF) were stable for many months. Previous studies have shown that Multisol (48.5% H2O, 40% propylene glycol, 10% ethanol, and 1.5% benzyl alcohol) provides stable solutions of GA. We confirmed the stability of GA in Multisol with phosphorus nuclear magnetic resonance (P NMR) and developed a method for the analysis of GA in Multisol using gas chromatographic flame photometric detection (GCFPD) in the phosphorus mode. The GC method used acetonitrile (CH3CN) for a dilution solvent because of its miscibility with GA in chloroform (CHCl3) standards and GA in Multisol samples at 1% (v/v). Furthermore, the dilutions with CH3CN made the phosphorus mode interference peak present in CHCl3 analytically manageable, reduced the interferences of Multisol in the GC separation, and contributed to a safe and reliable analysis of GA at 20 μg/mL. We demonstrated the stability of GA in Multisol stored for more than a year at 70°C. This method contributes a suitable technique for the preparation and analysis of reliable solutions of GA in nerve agent medical research and demonstrates the extended stability of GA in Multisol.