Direct Gas-Phase Detection of Nerve and Blister Warfare Agents Utilizing Active Capillary Plasma Ionization Mass Spectrometry

Ultrasensitive direct gas-phase detection of chemical warfare agents (CWAs) is demonstrated utilizing active capillary plasma ionization and triple quadrupole mass spectrometry (MS) instrumentation. Four G-agents, two V-agents, and various blistering agents [including sulfur mustard (HD)] were detected directly in the gas phase with limits of detection in the low parts per trillion (ng m⁻³) range. The direct detection of HD was shown for dry carrier gas conditions, but signals vanished when humidity was present, indicating a possible direct detection of HD after sufficient gas-phase pretreatment. The method provided sufficient sensitivity to monitor directly the investigated volatile CWAs way below their corresponding minimal effect dose, and in most cases even below the eight hours worker exposure concentration. In general, the ionization is very soft, with little to no in-source fragmentation. Especially for the G-agents, some dimer formation occurred at higher concentrations. This adds complexity, but also further selectivity, to the corresponding mass spectra. Our results show that the active capillary plasma ionization is a robust, sensitive, “plug and play” ambient ionization source suited (but not exclusively) to the very sensitive detection of CWAs. It has the potential to be used with portable MS instrumentation.