Development of Soft-Ionization for Particulate Organic Detection with the Aerodyne Aerosol Mass Spectrometer

75716-Aerosol particles in the atmosphere have important effects on visibility, acid deposition, climate, and human health. A significant part of anthropogenic aerosols is generated from energy-related activities, and organic compounds are known to constitute a significant fraction of ambient aerosol mass in many locations. However the measurement of the chemical composition of organic aerosols is ¿dismal,¿ according to a recent source, and real-time, size-resolved, quantitative instruments are required. A recently developed aerosol mass spectrometer (AMS), which uses electron impact ionization and quadrupole mass spectrometry, has shown potential; however, the electron impact ionization causes fragmentation of molecules, making it difficult to identify the chemical species, especially the organic component. This project will replace standard electron impact ionization with two less energetic (softer) ionization approaches: Lithium Ion Attachment and UV Photo-ionization. These methods will extend the chemical selectivity of the aerosol mass spectrometer and improve the identification of organic species. In Phase I, the low energy ionization sources will be developed, constructed, and fitted to the AMS for laboratory testing. The analytical sensitivity and selectivity of the instrument towards different classes of organic compounds will be assessed and compared with results obtained using the conventional ¿hard¿ electron impact ionization source. Commercial Applications and Other Benefits as described by the awardee: The instrument should have application in ambient pollution monitoring, chemical and biological warfare agent identification, and the characterization and control of aerosol emissions from a variety of industrial and energy production processes (which produce aerosol-laden gaseous exhaust or waste streams).