American Association for Aerosol Research - Abstract Submission

AAAR 36th Annual Conference
October 16 - October 20, 2017
Raleigh Convention Center
Raleigh, North Carolina, USA

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Synthesis of Four Monoterpene-derived Organosulfates and their Quantification in Atmospheric Aerosol Samples

YUCHEN WANG, Jingyun Ren, X.H. Hilda Huang, Rongbiao Tong, Jianzhen Yu, Hong Kong University of Science and Technology

     Abstract Number: 167
     Working Group: Carbonaceous Aerosols in the Atmosphere

Abstract
Monoterpenes, a major class of biogenic volatile organic compounds (VOCs), are known to produce oxidation products that further react with sulfate to form organosulfates. Such a class of secondarily formed aerosol products involving anthropogenic sulfur precursor represent controllable secondary organic aerosol from biogenic VOCs. The accurate quantification of monoterpene-derived organosulfates (OSs) is necessary for quantifying this aerosol source; however, it has been hampered by a lack of authentic standards. In this work, we report a unified synthesis strategy of monoterpene-derived OSs from the respective monoterpene through Upjohn dihydroxylation and mono-sulfation with sulfur trioxide-pyridine complex. We demonstrate the successful synthesis of four monoterpene-derived OS compounds, including α-pinene OS, β-pinene OS, limonene OS and limonenaketone OS. Quantification of OSs is commonly achieved using liquid chromatography-mass spectrometry (LC-MS) by either monitoring the [M-H]- ion or through multiple reaction monitoring (MRM) of mass transitions between the [M-H]- and m/z 97 ions. Comparison between the synthesized standards and previously adopted quantification surrogates reveals that camphor-10-sulfonic acid is a better quantification surrogate using [M-H]- as the quantification ion while the highly compound-specific nature of MRM quantification makes it difficult to choose a suitable surrogate. Both could be rationalized in accordance to their respective MS quantification mechanisms. The in-house availability of the authentic standards enables us to discover that β-pinene OS, due to the sulfate group at the primary carbon, partially degrades to a dehydrogenated OS compound during LC/MS analysis and a hydroperoxy OS over a prolonged storage period (> 5 month). Limonene OS was positively identified for the first time in ambient samples and found to be more abundant than α-/β-pinene OS in the Pearl River Delta, China. This work highlights the critical importance of having authentic standards in advancing our understanding of the interactions between biogenic VOC emissions and anthropogenic sulfur pollution.