The sensitivity of benzene cluster cation chemical ionization mass spectrometry to select biogenic terpenes

Autor: A. Lavi, M. P. Vermeuel, G. A. Novak, T. H. Bertram
Jazyk: angličtina
Rok vydání: 2018
Předmět:
Zdroj: Atmospheric Measurement Techniques, Vol 11, Pp 3251-3262 (2018)
Druh dokumentu: article
ISSN: 1867-1381
1867-8548
DOI: 10.5194/amt-11-3251-2018
Popis: Benzene cluster cations are a sensitive and selective reagent ion for chemical ionization of select biogenic volatile organic compounds. We have previously reported the sensitivity of a field deployable chemical ionization time-of-flight mass spectrometer (CI-ToFMS), using benzene cluster cation ion chemistry, for detection of dimethyl sulfide, isoprene and α-pinene. Here, we present laboratory measurements of the sensitivity of the same instrument to a series of terpenes, including isoprene, α-pinene, β-pinene, D-limonene, ocimene, β-myrcene, farnesene, α-humulene, β-caryophyllene, and isolongifolene at atmospherically relevant mixing ratios (5H8 ⋅ C6H6+) with a sensitivity ranging between 4 and 10 ncps ppt−1, which depends strongly on the reagent ion precursor concentration, de-clustering voltages, and specific humidity (SH). Monoterpenes are detected primarily as the molecular ion (C10H16+) with an average sensitivity, across the five measured compounds, of 14 ± 3 ncps ppt−1 for SH between 7 and 14 g kg−1, typical of the boreal forest during summer. Sesquiterpenes are detected primarily as the molecular ion (C15H24+) with an average sensitivity, across the four measured compounds, of 9.6 ± 2.3 ncps ppt−1, that is also independent of specific humidity. Comparable sensitivities across broad classes of terpenes (e.g., monoterpenes and sesquiterpenes), coupled to the limited dependence on specific humidity, suggest that benzene cluster cation CI-ToFMS is suitable for field studies of biosphere–atmosphere interactions.
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