Abstract

Single particles are detected on the fly by laser desorption mass spectrometry. Particles entering the source region of the mass spectrometer scatter radiation from a helium-neon laser beam. The scattered radiation triggers an excimer laser, causing one step laser desorption and ionization of the particle. A complete mass spectrum is subsequently recorded with a time-of-flight mass analyzer. Aerosols are sampled from atmospheric pressure through a two-stage differentially pumped inlet. Since the particle transit time in the vacuum prior to analysis is small, evaporation of volatile components is minimized. We have used rapid single-particle mass spectrometry to detect both inorganic and organic species.¹ When a relatively low irradiance for laser desorption is used, incomplete ablation of the particle occurs and material located near the surface is preferentially sampled. Higher laser irradiances sample a greater fraction of the entire particle. Potential applications include the analysis of airborne particulate matter and the detection of trace species adsorbed to suspended microparticles in solution.

© 1992 Optical Society of America