AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Ambient Inlet Ionization for On-Line Molecular Characterization of Aerosols
ANDREW J. HORAN, Murray Johnston, University of Delaware
Abstract Number: 326 Working Group: Instrumentation and Methods
Abstract The ability to determine the molecular composition of aerosol particles in near real-time is crucial to understanding the rates and mechanisms of reactions leading to their formation. In order to perform such an analysis, factors contributing to ionization efficiency reduction need to be thoroughly mitigated. To this end, a novel on-line source has been developed by modifying several inlet ionization techniques. Drawing from elements of Extractive Electrospray Ionization (EESI) and Solvent Assisted Inlet Ionization (SAII), an aerosol sample is passed over the evaporating droplets of a SAII liquid flow containing only solvent. The interaction between the aerosol and the SAII ‘plume’ is fully contained within the heated inlet of a quadrupole-time-of-flight (QTOF) mass analyzer and both positive and negative ions can be detected. The positive ion spectrum is typically dominated by M+Na$^+ ions, while the negative ion spectrum is dominated by M-H$^- ions. In this setup, the entirety of the aerosol passes into the mass spectrometer, reducing losses from inefficient ionization that are present in other on-line methods. The use of a QTOF mass analyzer not only produces molecular information, but MS/MS can also be employed to determine structural information in real time. In this way, a sensitive technique is developed that allows for real-time characterization, of atmospherically relevant aerosol systems. The method is demonstrated by analyzing standard aerosols as well as a sample of secondary organic aerosol created by the ozonolysis of volatile organic carbon precursors. The effect of changing the composition of the SAII solvent is also examined.