High Chemical Resolution Analysis of Atmospheric Organic Aerosol Using a Novel Thermal Desorption Gas Chromatograph infiTOF Mass Spectrometer (TD-GC-infiTOF)

MICHAEL WALKER, Siqin He, Minoru Kano, Brent Williams, Washington University in St. Louis

     Abstract Number: 382
     Working Group: Instrumentation and Methods

Abstract
Advances in mass spectrometry (MS) measurement techniques have been central to an increased understanding in the chemical composition of organic aerosol (OA) in the atmosphere. Coupling thermal desorption – gas chromatography (TD-GC) methods with MS allows for the separation of thousands of compounds in OA, but many of the detected compounds are not within existing databases, making identification challenging. High resolution mass spectrometers provide additional insight to the molecular formulas of any detected ions, but the resolution of field-deployable time-of-flight (TOF) mass spectrometers is often insufficient to fully characterize complex samples.

In order to overcome these challenges, an infiTOF mass spectrometer has been coupled to a TD-GC system to characterize complex environmental samples. The infiTOF can achieve very high resolution (~40,000) in a small footprint by sending ions through a tunable number of loops within the TOF region of the instrument. This approach allows for an operator to achieve high sensitivity measurements at lower MS resolution, or conversely lower sensitivity measurements at higher resolution to aid in the identification of unknown compounds. A range of chemical standards are used for the initial characterization of the TD-GC-infiTOF instrument to optimize the operating conditions that maximize the performance of the mass spectrometer in characterizing the eluting compounds. Furthermore, complex samples (e.g., biomass burning aerosol) are analyzed under the low- and high-resolution operating modes to demonstrate the strengths of the variable resolution offered by the TD-GC-infiTOF.