Photoionization induced chemical ionization time-of-flight mass spectrometry for rapid and sensitive detection of trace gaseous chemical warfare agents.

On-site accurate and real-time monitoring of trace chemical warfare agents is a critical component of national security surveillance. In this study, a photoionization-induced chemical ionization time-of-flight mass spectrometry is developed for the detection of trace gaseous chemical warfare agents under ambient conditions. Firstly, a benzene-toluene-xylene mixture standard gas is utilized to optimize the instrument parameters, followed by screening of dopants for chemical warfare agents detection, with methanol ultimately identified as the optimal dopant. The limit of detection for chemical warfare agents-related simulants, including 2-chloroethyl ethyl sulfide, dimethyl methyl phosphonate, toluene, diisopropyl methyl phosphonate, tributyl phosphate, and triethyl phosphate, are determined to be 38 ng·m-3, 6.59 ng·m-3, 79 ng·m-3, 27 ng·m-3, 259 ng·m-3, and 35 ng·m-3, respectively, within a 1 s acquisition time. For authentic chemical warfare agents, the limit of detection of O-isopropyl methyl phosphonofluoridate, bis(2-chloroethyl) sulfide, and O-Butyl S-[2-(diethylamino)ethyl] methyl phosphonothioate within 1 s are 137 ng·m-3, 166 ng·m-3, and 563 ng·m-3, respectively, with linear correlation coefficient R2 all exceeding 0.90. Notably, extending the acquisition time significantly enhanced the signal-to-noise ratio for trace chemical warfare agents; for example, the signal-to-noise ratio of O-Butyl S-[2-(diethylamino)ethyl] methyl phosphonothioate detected over 10 s is 6.8-fold higher than that of a 1 s measurement. Comparing to the previously reported results, the limit of detection of O-isopropyl methylphosphonofluoridate and bis(2-chloroethyl) sulfide achieved by photoionization-induced chemical ionization time-of-flight mass spectrometry within 1 s are improved by 1.2-6.5 times, and demonstrating that the superior speed and sensitivity for hazardous exposure evaluation at lower levels of chemical warfare agents.