Direct detection of chemical warfare agent simulants in soil by thermal desorption-low temperature plasma-mass spectrometry

Abstract For the rapid, accurate and real-time detection of trace chemical warfare agents in soil, direct detection of chemical warfare agent simulants in soil by thermal desorption-low temperature plasma ionization-mass spectrometry was developed. Multi-factor analysis of variance was used to quantitatively analyze the factors affecting the ionization efficiency of LTP based on the emission spectra of the plasma flame. The experimental parameters including the distance between LTP outlet and thermal desorption device, the flow rate of discharge gas, the temperature of ion source, the thermal desorption temperature and different solvents were optimized. Dimethyl methylphosphonate (DMMP, G-series nerve agent simulant), tributyl phosphate (TBP, V-series nerve agent simulant) and 2-Chloroethyl ethylsulfide (CEES, H-series blister agent simulant) were desorbed and ionized, forming the typical positive ions of [DMMP + H]+, [DMMP-HOCH3+H]+, [TBP + H]+, [TBP-3(C4H8)+H]+ and [CEES-Cl]+, [CEES- C2H4Cl]+. The ions were analyzed using the multiple reaction monitoring (MRM) of triple quadrupole mass spectrometer. Detection limit of the method was 5 pg for DMMP (m/z 125 > 93, S/N 3:1), 5 pg for TBP (m/z 267 > 99, S/N 3:1) and 5 ng for CEES (m/z 89 > 61, S/N 3:1). Trace level of CWA simulants can be directly detected with simple sample pretreatment, suggesting that the TD-LTP-MS method is useful for quick and direct detection of chemical warfare agents in soil.