Thermal Desorption Comprehensive Two-Dimensional Gas Chromatography: An Improved Instrument for In-Situ Speciated Measurements of Organic Aerosols

摘要

The organic fraction is a major constituent of fine atmospheric particulate matter, though its chemical composition is complex and not well understood. This complexity presents an extreme analytical challenge and is well suited to analysis by comprehensive two-dimensional gas chromatography (GC x GC). This has recently been coupled to a thermal desorption aerosol gas (TAG) chromato-graph instrument to provide improved in-situ, hourly measurement of speciated organic compounds in atmospheric aerosols (ID-TAG). The original 2D-TAG instrument utilized a flame ionization detector, dual-stage modulator, and a second-dimension column that proved to be thermally unstable under optimal analysis conditions, which limited compound identification, instrument robustness, and time resolution. In this paper, we address these shortcomings by demonstrating the successful integration of a time-of-flight mass spectrometer (TOFMS), development of a simplified hybrid thermo-pneumatic modulator, and incorporation of a more thermally stable secondary column. These improvements resulted in an instrument capable of providing detailed speciated information of organic tracer compounds in atmospheric aerosols in near real time.