Volatility and Polarity Separated (VAPS) Total Organic Aerosol using Thermal Desorption Modulated Chromatography

Aerosol particles have important impacts on visibility, acid deposition, climate, and human health, although large uncertainties remain in quantifying their chemical composition and atmospheric transformations. A large fraction of the anthropogenic aerosol is generated from energy- related activities, and organic compounds are known to constitute a significant fraction of ambient aerosol mass. Recently discovered discrepancies between measurements of organic aerosol mass and predictions from large scale atmospheric models suggest that our understanding of the sources of secondary organic aerosol is incomplete. This SBIR Phase II project addresses the critical need for the improved chemical characterization of organic aerosol in the atmosphere. This problem will be addressed through the development and testing of a novel instrument that combines separation of particulate organics based on volatility and polarity with high-resolution electron impact ionization mass spectrometry, allowing the identification of individual compounds, as well as measurement of key chemical characteristics, such as the oxygen-to- carbon ratio. Particles will be collected on an impactor and thermally desorbed into the detector. Temperature control of the sample desorption process will give information on the volatility of the organic compounds, a crucial element in understanding gas to particle conversion in the atmosphere. Desorbed material will pass through a short gas chromatography column and be separated based on polarity, another key property for molecular identification. The combination of volatility, polarity and high resolution mass spectrometry data will provide inputs to atmospheric models and improve our understanding of the sources and transformations of organic aerosol. The Phase I project succesfully demonstrated the feasibility of the instrumental approach. The ability to separate organic aerosol constituents on both a volatility and polarity basis was demonstrated and optimized through laboratory experiments. The volatility and polarity separated material was successfully detected with a high resolution mass spectrometer. During Phase II, a commercial version of the instrument will be developed. Specific tasks include improving temperature control of the collection and transfer components, developing new data acquisition and data analysis tools, and developing automatic calibration procedures. The new instrument will be tested in the laboratory and in a field deployment where results can be compared and contrasted with other measurement techniques. Commercial Applications and Other Benefits: The primary market for this instrument will be atmospheric research groups at universities and national laboratories, including DOE facilities. In addition, the instrument will be well-suited for environmental monitoring, as well as for the characterization of emissions from a variety of industrial and energy production processes. The instrument developed in this program will yield a significant level of direct commercial sales and contract field measurements in the atmospheric science and environmental pollution research and development communities.