Direct Mass Spectrometric Detection of VX, RVX, and Novichok A-Series Nerve Agents for Screening Contaminated Sites...

After a chemical terrorist attack involving nonvolatile and persistent nerve agents with extremely high dermal toxicity, rapid identification of the contaminated area and confirmation of decontamination is important. A method for swabbing surfaces suspected of contamination and conducting screening analysis for the presence of nerve agents will facilitate rapid completion of decontamination activities. In this study, a commercially available nano liquid chromatograph/high-resolution mass spectrometer was modified at low cost to develop an ambient ionization mass spectrometer with atmospheric pressure corona discharge ionization (APCDI) capabilities. The detection performance of the system for nonvolatile nerve agents (VX, RVX, A-230, A-232, A-234, A-242, and A-262) was examined. Monoisotopic peaks of the protonated molecules and their characteristic product ion spectra were observed for all tested compounds. For VX, A-230, and A-242, the detection limits when monitoring the monoisotopic peaks ranged from 0.025 to 0.25 ng. Novichok compounds exhibited higher sensitivity than VX or RVX, although the calculated gas phase basicity values showed little difference among the compounds. Peak intensity reproducibility showed intraday variation of 4.32-31.1% and interday variation of 8.95-44.1%. For samples collected on foam polyethylene swabs, the detection limits of the protonated molecules of VX, A-230, and A-242 were 10-100 ng for samples collected from stainless steel surfaces. This detection limit range is sufficient for screening of contaminated areas. When investigating the sample stability on swabs after collection, we found VX and A-230 remained detectable for 7 days and A-242 remained detectable for 3 days after swabbing of 1000 ng from a stainless steel surface. This developed analytical system is considered suitable for off-site analysis.