Revisiting benzene cluster cations for the chemical ionization of dimethyl sulfide and select volatile organic compounds

TitleRevisiting benzene cluster cations for the chemical ionization of dimethyl sulfide and select volatile organic compounds
Publication TypeJournal Article
Year of Publication2016
AuthorsKim MJ, Zoerb M.C, Campbell N.R, Zimmermann K.J, Blomquist B.W, Huebert B.J, Bertram TH
JournalAtmospheric Measurement Techniques
Date Published2016/05
Type of ArticleArticle
ISBN Number1867-1381
Accession NumberWOS:000375616100004
Keywordsaerosol; ambient air; atmospheric-pressure; molecules; photoionization; ptr-ms; reaction-mass-spectrometry; sesquiterpenes; spectroscopy; water

Benzene cluster cations were revisited as a sensitive and selective reagent ion for the chemical ionization of dimethyl sulfide (DMS) and a select group of volatile organic compounds (VOCs). Laboratory characterization was performed using both a new set of compounds (i.e., DMS, beta-caryophyllene) as well as previously studied VOCs (i.e., isoprene, alpha-pinene). Using a field deployable chemical-ionization time-of-flight mass spectrometer (CI-ToFMS), benzene cluster cations demonstrated high sensitivity (>1 ncps ppt(-1))to DMS, isoprene, and alpha-pinene standards. Parallel measurements conducted using a chemical-ionization quadrupole mass spectrometer, with a much weaker electric field, demonstrated that ion-molecule reactions likely proceed through a combination of ligand-switching and direct charge transfer mechanisms. Laboratory tests suggest that benzene cluster cations may be suitable for the selective ionization of sesquiterpenes, where minimal fragmentation (<25 %) was observed for the detection of beta-caryophyllene, a bicyclic sesquiterpene. The in-field stability of benzene cluster cations using CI-ToFMS was examined in the marine boundary layer during the High Wind Gas Exchange Study (HiWinGS). The use of benzene cluster cation chemistry for the selective detection of DMS was validated against an atmospheric pressure ionization mass spectrometer, where measurements from the two instruments were highly correlated (R-2 > 0.95, 10 s averages) over a wide range of sampling conditions.

Short TitleAtmos. Meas. Tech.
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