We have built a particle analyzer capable of real-time detection and characterization of individual particles. Particle analysis is accomplished by pulsed laser ablation of a particle followed by time-of-fiight mass spectrometry of the resulting atomic and molecular ions. The detected ions are characteristic of a particle's

ABSTRACT. Composition and size of individual submicron particles have been measured us ing a laser atomization r r r r r ionization mass spectrometry technique, the Particle Blaster. Individual particles are quantitatively converted to atomic cations, providing information on both their complete elemental composition and particle size. Measured average atomic ratios for ; 100 nm particles of sodium chloride is ( ) ( ) 1.12 " 0.36 Cl:Na , for 50 nm particles of silica is 1.93 " 0.52 O:Si , and for 64 ( ) ( ) nm polystyrene latex spheres PSL is 1.13 " 0.19 H:C , in excellent agreement with the empirical formulae. Calculated particle sizes agree well with electrostatic classi er or TEM measurements in the size range of 17-900 nm diameter for particles of sodium chloride, silicon, and PSL. Size distributions are also obtainable, giving narrower distributions than are measured with an electrostatic classier, for particles of alumina, silica, sodium chloride, and PSL spheres. Comparison with TEM data shows comparable primary particle s izes, but numerous particle aggregates are detected by the Particle Blaster which are unreported by the TEM measurements.

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Advances in instrumentation used for particle compositional analysis have enabled real-time identification and classification of individual particles. However, precise quantitation of individual particle compositions has been elusive. Here, we demonstrate that real-time quantitative single-particle compositional analysis is possible. This is illustrated for individual particles of sodium chloride (70 nm), ammonium sulfate (70 nm), and silica (40-2000 nm) using a real-time aerosol mass spectrometer. Atomic fractions for major components (> 1% concentration) of individual multicomponent particles have been measured within +/-20% accuracy. Trace element detection limits of 20 ppm are also demonstrated when individual particle compositions are ensemble averaged.