COUPLING 2-STEP LASER DESORPTION IONIZATION WITH AEROSOL TIME-OF-FLIGHT MASS SPECTROMETRY FOR THE ANALYSIS OF INDIVIDUAL ORGANIC PARTICLES/

Analysis of organic compounds in aerosol particles using real-time sin gle Fat-tide techniques is difficult because of extensive fragmentatio n that occurs in the laser desorption/ionization step. In an effort to avoid such fragmentation processes, we coupled a ''soft'' two-step la ser desorption/ionization technique (L2MS) with aerosol time-of-flight mass spectrometry (AT-OFMS). Ln these studies, we find this combinati on preserves intact organic molecules while providing the real-time ma ss spectra of suspended aerosol particles. Mass spectra of particles a nalyzed by one-step desorption mass spectrometry and L2MS are presente d for comparison. These include 2,4-dihydroxybenzoic acid as a test ca se and wood and cigarette combustion particles as real world examples. This is the first published demonstration of L2MS performed on single particles not deposited on a substrate prior to analysis. (C) 1998 Am erican Society for Mass Spectrometry.