Gentle photoionization of organic constituents using vacuum ultraviolet aerosol mass spectrometry Public Deposited

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  • March 20, 2019
Creator
  • Mysak, Erin R.
    • Affiliation: College of Arts and Sciences, Department of Chemistry
Abstract
  • Aerosol particles have long been a primary focus of the atmospheric community due to their influence on human health, radiative forcing, and participation in atmospheric chemistry. Conventionally, aerosols have been collected on filters and analyzed off-line by GC-MS, LC-MS, and FTIR. These techniques made valuable inroads to particle speciation, however, the inherent physical and chemical artifacts during sampling initiated the development of a succession of on-line aerosol mass spectrometers. Currently, a variety of real-time aerosol mass spectrometers, many with single particle analysis capabilities, have been developed and installed in laboratories as well as in the field. Atmospheric aerosols are complex mixtures of inorganic and organic species, and whereas analysis of inorganics is rather straightforward due to their robust nature, organics are fragile and analysis is challenging. Several researchers have moved specifically towards analysis of organic aerosol particles, attempting to simplify peak assignment by reducing the fragmentation of these delicate molecules. The initial portion of this project involved design and development of an aerosol mass spectrometer, ideal for analyzing a wide size range of organic aerosol particles. The novel mass spectrometer uses both continuous vaporization with a cartridge heater and quasiiv continuous photoionization by tunable vacuum ultraviolet light produced by synchrotron radiation. Coupling continuous vaporization and ionization techniques with a high brightness photon source allows analysis of ultrafine aerosol particles, which have high toxicity and high number concentration in ambient air. Several atmospherically relevant organic molecules are examined, along with a more complex yet more realistic secondary organic aerosols formed from terpene ozonolysis. Finally, a timing circuit used to analyze single particles (diameter > 200nm) was designed and developed. The versatile electronic circuit can be used to couple multi-laser systems having pre-triggering requirements to single particle arrival in the ionization region of the mass spectrometer. It can also be applied to continuous vaporization and ionization schemes where one wants to pulse ions into a time of flight analyzer as particles arrive in the interaction region.
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  • Baer, Tomas
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