Two portable aerosol time-of-flight mass spectrometers (ATOFMS) of identical design are described. These instruments are powerful new tools for providing temporal and spatial information on the origin, reactivity, and fate of atmospheric aerosols. Each is capable of analyzing the size and composition of individual particles from a polydisperse aerosol in real-time. Particles are introduced into the instrument through a particle beam interface, sized by measuring the delay time between two scattering lasers, and compositionally analyzed using a dual-polarity laser desorption/ionization time-of-flight mass spectrometer. These are the first dual-ion TOFMS instruments to utilize a dual reflectron design. The instruments measure 72 in. long × 28 in. wide × 60 in. high and weigh ∼500 lb. Pneumatic tires allow them to be transported through standard doorways, elevators, and handicap ramps, granting access to virtually any location. Furthermore, because of rugged construction they will be able to operate during transport by automobile, boat, or aircraft.

The heterogeneous replacement of chloride by nitrate in individual sea-salt particles was monitored continuously over time in the troposphere with the use of aerosol time-of-flight mass spectrometry. Modeling calculations show that the observed chloride displacement process is consistent with a heterogeneous chemical reaction between sea-salt particles and gas-phase nitric acid, leading to sodium nitrate production in the particle phase accompanied by liberation of gaseous HCl from the particles. Such single-particle measurements, combined with a single-particle model, make it possible to monitor and explain heterogeneous gas/particle chemistry as it occurs in the atmosphere.

The rapid chemical analysis of individual cells is an analytical capability that will profoundly impact many fields including bioaerosol detection for biodefense and cellular diagnostics for clinical medicine. This article describes a mass spectrometry-based analytical technique for the real-time and reagentless characterization of individual airborne cells without sample preparation. We characterize the mass spectral signature of individual Bacillus spores and demonstrate the ability to distinguish two Bacillus spore species, B. thuringiensis and B.atrophaeus, from one another very accurately and from the other biological and nonbiological background materials tested with no false positives at a sensitivity of 92%. This example demonstrates that the chemical differences between these two Bacillus spore species are consistently and easily detected within single cells in seconds.