There is a growing concern that airborne particulate matter could be a greater health hazard then previously thought. Most of the research findings have been based either on the gross particle concentrations, sorted by size, independent of composition, or on bulk chemical analyses of particles collected on filters. Pete Reilly, Rainer Gieray, Mo Yang, Bill Whitten, and Mike Ramsey have been developing an instrument that can analyze airborne microparticles individually in real time in an ion trap mass spectrometer (see photo). With this instrument, particles bearing small quantities of harmful substances can be analyzed with high sensitivity in the presence of large numbers of normal background particles. Air containing the particles, whether dust, pollen, microorganisms, or spores, is sucked into a chamber where the individual particles are detected and analyzed by laser ablation mass spectrometry. Once set up, the apparatus can operate unattended to serve as a real-time monitor of air quality. It has even greater importance, however, as an analytical instrument, where the power of ion trap mass spectrometry can be exploited for the characterization of particles from many sources.

Applications under current investigation include monitoring background levels of airborne bacteria and environmental monitoring in the vicinity of nuclear facilities. The researchers have shown, for example, that uranium can be detected in a particle of picogram mass containing fewer than 3000 uranium atoms (subattogram). Studies of carcinogenic polycyclic aromatic hydrocarbon compounds in soot particles and chemical substances that are important constituents of urban smog are also underway. Pete Reilly and Reiner Gieray are shown collecting diesel engine exhaust particles for analysis in the laboratory. With a slight modification of the apparatus, waterborne particles can be individually characterized as well, permitting high-sensitivity analysis of ground water and sediments for substances of low solubility.

References

M. Yang, P. T. A. Reilly, K. B. Boraas, W. B. Whitten, and J. M. Ramsey, "Real-Time Chemical Analysis of Aerosol Particles using an Ion Trap Mass Spectrometer", Rapid Commun. In Mass Spectrom. 10, 347-351 (1996).

P. T. A. Reilly, R. A. Gieray, M. Yang, W. B. Whitten, and J. M. Ramsey, "Tandem Mass Spectrometry of Individual Airborne Microparticles", Anal. Chem. 69, 36-39 (1997).

R. A. Gieray, P. T. A. Reilly, M. Yang, W. B. Whitten, and J. M. Ramsey, "Real-Time Detection of Individual Airborne Bacteria", J. Microbiol. Methods 29, 191-199 (1997).

R. A. Gieray, P. T. A. Reilly, M. Yang, W. B. Whitten, and J. M. Ramsey, "Tandem Mass Spectrometry of Uranium and Uranium Oxides in Airborne Particulates", Anal. Chem. 70, 117-120 (1998).