title: Identification of hydroxy- and keto-dicarboxylic acids in remote marine aerosols using gas chromatography/quadruple and time-of-flight mass spectrometry.
abstract: BACKGROUND
  The identification of hydroxy- and keto-dicarboxylic acids (diacids) in remote marine aerosol samples is important for a better understanding of the composition of organic particulate matter, as this chemical composition is essential for predicting the effects on climate, air quality, and human health. Molecular characterization of these compounds provides insights into sources and formation pathways of organic aerosols.
  
  
  METHODS
  The method of chemical derivatization followed by gas chromatography-flame ionization detection (GC-FID), gas chromatography/quadruple mass spectrometry (GC/QMS) and gas chromatography/time-of-flight mass spectrometry (GC/TOFMS) was used to identify hydroxy- and keto-diacids in remote marine aerosols. Atmospheric samples were collected at Chichijima Island in the western North Pacific and the diacids and related compounds were extracted with organic-free ultrapure water. A two-step derivatization technique was employed, using 14% BF3 /n-butanol for the butylation of carboxyl groups and acidic ketones followed by N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) for the trimethylsilylation of hydroxyl groups.
  
  
  RESULTS
  Several new peaks were detected in the gas chromatogram after trimethylsilylation of the dibutyl ester fraction. Based on mass spectral interpretation with authentic standards, we successfully identified and quantified a homologous series of hydroxydiacids, including tartaric and oxaloacetic acids. In addition, transformation of oxaloacetic acid into its enol form was elucidated.
  
  
  CONCLUSIONS
  Utilizing GC-FID, GC/QMS and GC/TOFMS, hydroxy- and keto-diacids were identified in the remote marine aerosols. A complete structural characterization was achieved with extensive mass spectral analysis. Molecular distributions of hydroxydiacids generally showed the predominance of malic acid followed by tartronic acid. We consider that these hydroxydiacids are important intermediates in the atmospheric oxidation of organic aerosols to result in smaller diacids. Copyright © 2016 John Wiley & Sons, Ltd.
authors.affiliation: Graduate School of Environmental Science, Hokkaido University, Japan.|Institute of Low Temperature Science, Hokkaido University, Japan.
authors.forename: Divyavani
authors.initials: D
authors.lastname: Gowda
authors.affiliation: Institute of Low Temperature Science, Hokkaido University, Japan.
authors.forename: Kimitaka
authors.initials: K
authors.lastname: Kawamura
authors.affiliation: Institute of Low Temperature Science, Hokkaido University, Japan.
authors.forename: Eri
authors.initials: E
authors.lastname: Tachibana
mesh_terms: D003998:Dicarboxylic Acids / Q000032:analysis* / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D006880:Hydroxy Acids / Q000032:analysis* / Q000737:chemistry; D052638:Particulate Matter / Q000032:analysis* / Q000737:chemistry
chemical_list: D003998:Dicarboxylic Acids; D006880:Hydroxy Acids; D052638:Particulate Matter