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| Titel |
Understanding evolution of product composition and volatility distribution through in-situ GC×GC analysis: a case study of longifolene ozonolysis |
| VerfasserIn |
G. Isaacman, D. R. Worton, N. M. Kreisberg, C. J. Hennigan, A. P. Teng, S. V. Hering, A. L. Robinson, N. M. Donahue, A. H. Goldstein |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 11, no. 11 ; Nr. 11, no. 11 (2011-06-09), S.5335-5346 |
| Datensatznummer |
250009806
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| Publikation (Nr.) |
 copernicus.org/acp-11-5335-2011.pdf |
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| Zusammenfassung |
| A method for predicting volatility and polarity based on chromatographic
information was developed and applied to the smog chamber ozonolysis of the
sesquiterpene longifolene. The products were collected and analyzed using a
GC × GC Thermal Desorption Aerosol Gas Chromatograph/Mass Spectrometer
(2D-TAG) and a quadrupole Aerodyne Aerosol Mass Spectrometer (AMS). All the
secondary organic aerosol (SOA) was produced within the first half hour of
the experiment. However, the oxidation level of the organic aerosol, as
inferred from the fraction of ion m/z 44, suggested continued evolution of the
SOA over the subsequent hours. Measurements of speciated organic compounds
using 2D-TAG confirm that the composition of the particles changed over the
course of the experiment. Nearly 200 oxidation products (thought to be
mostly ketones and acids) were observed with 2D-TAG, but most could not be
identified definitively due to a lack of standards and the absence of likely
sesquiterpene oxidation products in available mass spectral databases. To
categorize the observed products, the vapor pressure and oxygen-to-carbon
ratio (O/C) of observed compounds were estimated based on their
two-dimensional chromatographic retention times relative to those of known
standards, establishing a retention time correlation (RTC) method for using
2D-TAG to better constrain important modelling parameters. The product
distribution continuously evolved in volatility and oxygenation during 5 h of oxidation. Using peak area as the best available proxy for mass, we
conclude that the product mixture includes many non-negligible products; the
most abundant 3 compounds accounted for only half of the total observed peak
area and 80 % of peak area was spread across 15 compounds. The data
provide evidence for three conclusions: (1) 2D-TAG provides valuable
volatility and oxygenation information even in the absence of definitive
species identification, (2) complex particle-phase chemistry causes continued
evolution of particle composition after new particles formation, and (3) minor products contribute significantly to SOA from the ozonolysis of longifolene. |
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