Development of a detection system for gas-phase aromatics and other molecules ionizable by soft X-rays demonstrated using methyl salicylate

In the present study, we developed the detection method for gas-phase aromatics and other molecules ionizable by soft X-rays demonstrated using methyl salicylate which is one of the chemical warfare agent simulants by using soft X-ray and aerosol measurement techniques. The aromatic chemical compounds which have the benzene ring are well detected by the soft X-ray assisted detection method which converts gas vapors to nanoparticles through the photochemical processes. The present study reports on the formation of nanoparticles by describing the stage change during the soft X-ray irradiation: particle-free mode; nucleation mode; transition mode; accumulation mode; and stable mode. In a controlled environment, the empirical calibration curves can predict ppbv-level methyl salicylate vapor concentrations using particle number or volume concentration data obtained from the real-time aerosol detection instrument. We expect that this technology can be utilized for calibrating or intercomparing other instruments that measure methyl salicylate concentrations.