Identifying and correcting interferences to PTR-ToF-MS measurements of isoprene and other urban volatile organic compounds

作者：Matthew M. Coggon, Chelsea E. Stockwell, Megan S. Claflin, Eva Y. Pfannerstill, Lu Xu, J. B. Gilman, Julia M. Marcantonio, Cong Cao, Kelvin H. Bates, Georgios I. Gkatzelis, Aaron Lamplugh, Erin F. Katz, Caleb Arata, Eric C. Apel, Rebecca S. Hornbrook, Felix Piel, Francesca Majluf, D. R. Blake, Armin Wisthaler, Manjula R. Canagaratna, B. M. Lerner, Allen H. Goldstein, John Mak, C. Warneke · 年份：2023 · DOI：10.5194/egusphere-2023-1497 · 被引用次数：23 · 研究领域：Advanced Chemical Sensor Technologies、Atmospheric chemistry and aerosols、Mass Spectrometry Techniques and Applications

Abstract. Proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS) is a technique commonly used to measure ambient volatile organic compounds (VOCs) in urban, rural, and remote environments. PTR-ToF-MS is known to produce artifacts from ion fragmentation, which complicates the interpretation and quantification of key atmospheric VOCs. This study evaluates the extent to which fragmentation and other ionization processes impacts urban measurements of the PTR-ToF-MS ions typically assigned to isoprene (m/z 69, C5H8H+), acetaldehyde (m/z 45, CH3CHO+), and benzene (m/z 79, C6H6H+). Interferences from fragmentation are identified using gas-chromatography (GC) pre-separation and the impact of these interferences are quantified using ground-based and airborne measurements in a number of US cities, including Las Vegas, Los Angeles, New York City, and Detroit. In urban regions with low biogenic isoprene emissions (e.g., Las Vegas), fragmentation from higher carbon aldehydes and cycloalkanes emitted from anthropogenic sources may contribute to m/z 69 by as much as 50 % during the day, while the majority of the signal at m/z 69 is attributed to fragmentation during the night. Interferences are a higher fraction of m/z 69 during airborne studies, which likely results from differences in the reactivity between isoprene and the interfering species along with the subsequent changes to the VOC mixture at higher altitudes. For other PTR masses, including m/z 45 and m/z 79, interf...