Molecular characterization of organic aerosol using nanospray desorption/electrospray ionization mass spectrometry: CalNex 2010 field study

TitleMolecular characterization of organic aerosol using nanospray desorption/electrospray ionization mass spectrometry: CalNex 2010 field study
Publication TypeJournal Article
Year of Publication2013
AuthorsO'Brien RE, Laskin A, Laskin J, Liu S, Weber R, Russell LM, Goldstein AH
JournalAtmospheric Environment
Volume68
Pagination265-272
Date Published2013/04
Type of ArticleArticle
ISBN Number1352-2310
Accession NumberWOS:000315241100030
Keywordscalifornia; CalNex; chemical-composition; compounds; constituents; electrospray; identification; isoprene; Nano-DESI; nitrogen; Nitrogen-containing organic; Oligomers; Orbitrap; organosulfates; particles; SOA
Abstract

Aerosol samples from the CalNex 2010 field study were analyzed using high-resolution mass spectrometry (HR-MS) coupled to a nanospray desorption/electrospray ionization (nano-DESI) source. The samples were collected in Bakersfield, CA on June 22-23, 2010. The chemical formulas of over 850 unique molecular species were detected in the mass range of 50-400 m/z using positive mode ESI of aerosol samples in the 0.18-0.32 mu m size range. Our analysis focused on identification of two main groups: compounds containing only carbon, hydrogen, and oxygen (CHO), and nitrogen-containing organic compounds (NOC). The NOC accounted for 40% (by number) of the compounds observed in the afternoon, and for 52% in the early morning samples. By comparing plausible reactant-product pairs, we propose that over 50% of the NOC in each sample could have been formed through reactions transforming carbonyls into imines. The CHO only compounds were dominant in the afternoon suggesting a photochemical source. The average O/C ratios of all observed compounds were fairly consistent throughout the day, ranging from 0.33 in the morning to 037 at night. We conclude that both photooxidation and ammonia chemistry may play a role in forming the compounds observed in this mixed urban-rural environment. (c) 2012 Elsevier Ltd. All rights reserved.

DOI10.1016/j.atmosenv.2012.11.056
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