Hydroxydicarboxylic acids: Markers for secondary organic aerosol from the photooxidation of α-pinene

M. Claeys, R. Szmigielski, I. Kourtchev, P. Van Der Veken, R. Vermeylen, W. Maenhaut, M. Jaoui, T.E. Kleindienst, M. Lewandowski, J.H. Offenberg, E.O. Edney

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168 Citations (Scopus)


Detailed organic analysis of fine (PM2.5) rural aerosol collected during summer at K-puszta, Hungary from a mixed deciduous/coniferous forest site shows the presence of polar oxygenated compounds that are also formed in laboratory irradiated α-pinene/NOx/air mixtures. In the present work, two major photooxidation products of α-pinene were characterized as the hydroxydicarboxylic acids, 3-hydroxyglutaric acid, and 2-hydroxy-4-isopropyladipic acid, based on chemical, chromatographic, and mass spectral data. Different types of volatile derivatives, including trimethylsilyl ester/ether, methyl ester trimethylsilyl ether, and ethyl ester trimethylsilyl ether derivatives were measured by gas chromatography/mass spectrometry (GC/MS), and their electron ionization (EI) spectra were interpreted in detail. The proposed structures of the hydroxydicarboxylic acids were confirmed or supported with reference compounds. 2-Hydroxy-4-isopropyladipic acid formally corresponds to a further reaction product of pinic acid involving addition of a molecule of water and opening of the dimethylcyclobutane ring; this proposal is supported by a laboratory irradiation experiment with α-pinene/NOx/air. In addition, we report the presence of a structurally related minor α-pinene photooxidation product, which was tentatively identified as the C7 homolog of 3-hydroxyglutaric acid, 3-hydroxy-4,4-dimethylglutaric acid. The detection of 2-hydroxy-4-isopropyladipic acid in ambient aerosol provides an explanation for the relatively low atmospheric concentrations of pinic acid found during daytime in forest environments.

Original languageEnglish
Pages (from-to)1628–1634
Number of pages7
JournalEnvironmental Science and Technology
Issue number5
Publication statusPublished - 23 Jan 2007
Externally publishedYes


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