Particle generation of low vapor pressure analytes for an on-demand aerosol standard.

The continual or on-demand delivery of aerosol is important for sensor validation and the development of trace particle detection methodologies. The system presented here operates by introducing aerosolized analytical standard solutions in a heated air flow, generating vapor phase analytes that are subsequently transported and cooled to provide aerosolized particles. The notable design feature was a small concentric air flow device that blends chilled dry air with vapor phase analyte to induce a phase transition without the need for volatile organic solvents. While organic solvents accelerate solvent evaporation, they present potential interferences for downstream sensors. Cyclotrimethylenetrinitramine (RDX) particles were generated and optically counted from the exhaust plume aerosol. The solid RDX material was binned into 1–2.5, 2.5–5, 5–10, and 10+ µm diameter sizes and when the system was actively cooled, the generation of particles exhibited a relative increase of 4.9%, 27.6%, 95.6%, and 78.0% in production, respectively. When observed under a microscope, collected RDX particles ranged from about 1 to 7 µm in diameter. It was determined that the production of solid material was proportional to the temperature and mass loading of the vapor, as dictated by the feed solution concentration; cooler temperatures and higher concentrations led to the increased production of particles ranging from 1 to 10 μm in diameter for the low-vapor pressure analytes studied: RDX (cyclotrimethylenetrinitramine), PETN (pentaerythritol tetranitrate), TNT (2-methyl-1,3,5-trinitrobenzene), and 2,6-DNT (2,6-dinitrotoluene). [ABSTRACT FROM AUTHOR]