Aerosol Time-of-Flight Mass Spectrometry: A New Method for Performing Real-Time Characterization of Aerosol Particles

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Abstract
Recently our research group has developed aerosol time-of-flight mass spectrometry, an instrumental method for the real-time characterization of individual aerosol particles. Aerosol time-of-flight mass spectrometry couples two-laser aerodynamic particle sizing with time-of-flight mass spectrometry to measure both the size and composition of single particles. One of the aims of this research is to provide more detailed measurements of atmospheric aerosol particles than are currently available for epidemiological studies. Current aerosol data mainly consist of particle mass concentration measurements, which are employed to correlate particle concentration with effects on mortality and morbidity. Sample spectra of several different particle classifications are shown. Monitoring ambient aerosols over time demonstrates that significant changes in particle chemical composition can occur without correspondingly large changes in the total size distribution. Also, certain metal species (such as iron, lead, titanium, and vanadium) are found to be associated with specific compounds, perhaps providing direct indication on particle sources. A larger, more complete database of ambient aerosol measurements based on single particle analysis will provide a thorough foundation for more detailed and extensive epidemiological studies. For example, single particle analysis not only provides the means for measuring sulfates in the fine particle mode, but it may also determine which species are associated with the sulfates in individual particles.