Mass Spectrometric Determination of Chemical Warfare Agents in Indoor Sample Media Typically Collected During Forensic Investigations

Terrorist use of chemical warfare agents against civilian targets could involve the targeting of enclosed populated spaces. DRDC Suffield, in collaboration with the Royal Canadian Mounted Police, identified a need for analytical methods for chemical warfare agent identification in media, including flooring, wall surfaces, office fabrics and paper products, that would typically be collected in an office environment during forensic investigations. Typical office environment media were spiked at the 4 to 20 mug/g level with either a complex munitions grade sample of tabun (GA) or with a standard containing the three nerve agents, sarin (GB), cyclohexyl methylphosphonofluoridate (GF), soman (GD) and the nerve agent simulant, triethyl phosphate (TEP), to evaluate the potentials of LC-ESI-MS and LC-ESI-MS/MS for forensic purposes. The spiked chemical warfare agents were recovered with varying efficiencies, but in all cases sufficient chemical warfare agent was recovered for identification purposes. In some instances the aqueous extracts contained numerous co-extracted sample components that complicated LC-ESI-MS analysis and hampered identification. These interferences were minimized during LC-ES-MS/MS analysis, where each of the chemical warfare agents was identified on the basis of acquired product ion mass spectra. MS data for all the spiked compounds in the nerve agent standard and the munitions grade tabun were acquired in the continuum mode with a resolution of 9000, which typically resulted in mass measurement errors of 0.001 Da or less. Application of the developed sample handling and analysis methodology is anticipated during forensic investigations where evidence of chemical warfare agent use is required for criminal prosecution or to assess remediation/restoration efforts following an incident.