A HIGHLY SENSITIVE GAS CHROMATOGRAPHY - MASS SPECTROMETRY METHOD FOR THE ANALYSIS OF BIOGENIC TERPENES

Gas chromatography – mass spectrometry (GC/MS) analysis of biogenic volatile organic compounds (BVOCs) in ambient air have provided significant insights into terpene production, increasing our understanding of specific tree species emissions and the influence of the diurnal cycle. Studying biogenic production of isoprene based BVOCs and secondary organic aerosols (SOA) is important because these emissions react with anthropogenic emissions, affecting air quality and regional climate. However, terpene hydrocarbons pose difficulty for analysis because of the large number of known structures, their high reactivity, and their low occurrence in the atmosphere. This study specifically focused on the development of a highly sensitive GC/MS technique that is selective for the analysis of terpenes (monoterpenes and sesquiterpenes) and SOA formation in an anthropogenic-influenced region in the southeastern United States (US). Our GC/MS method utilizes simultaneous Scan and selective ion monitoring (SIM) modes allowing for low parts-per-trillion by volume (pptv) analyte detection limits. Terpenes emission from Eastern Red Cedar, Hickory Shagbark, Eastern Redbud, and Winged Elm trees were analyzed using this methodology. Our analysis gives evidence that Eastern Red Cedar species emits high quantities of terpenes and terpene concentrations fluctuate throughout the diurnal cycle for all species with no clear trend. This method can be a viable alternative to Proton Transfer Reaction – Mass Spectrometry for measuring low level terpenes in BVOCs studies.