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| Titel |
Application of high-resolution time-of-flight chemical ionization mass spectrometry measurements to estimate volatility distributions of α-pinene and naphthalene oxidation products |
| VerfasserIn |
P. S. Chhabra, A. T. Lambe, M. R. Canagaratna, H. Stärk, J. T. Jayne, T. B. Onasch, P. Davidovits, J. R. Kimmel, D. R. Worsnop |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 8, no. 1 ; Nr. 8, no. 1 (2015-01-05), S.1-18 |
| Datensatznummer |
250116034
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| Publikation (Nr.) |
 copernicus.org/amt-8-1-2015.pdf |
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| Zusammenfassung |
| Recent developments in high-resolution time-of-flight chemical ionization
mass spectrometry (HR-ToF-CIMS) have made it possible to directly detect
atmospheric organic compounds in real time with high sensitivity and with
little or no fragmentation, including low-volatility, highly oxygenated
organic vapors that are precursors to secondary organic aerosol formation.
Here, using ions identified by high-resolution spectra from an HR-ToF-CIMS
with acetate reagent ion chemistry, we develop an algorithm to estimate the
vapor pressures of measured organic acids. The algorithm uses identified ion
formulas and calculated double bond equivalencies, information unavailable in
quadrupole CIMS technology, as constraints for the number of possible oxygen-containing functional groups. The algorithm is tested with acetate chemical ionization mass
spectrometry (acetate-CIMS)
spectra of O3 and OH oxidation products of α-pinene and
naphthalene formed in a flow reactor with integrated OH exposures ranged
from 1.2 × 1011 to 9.7 × 1011 molec s cm−3,
corresponding to approximately 1.0 to 7.5 days of equivalent atmospheric
oxidation. Measured gas-phase organic acids are similar to those previously
observed in environmental chamber studies. For both precursors, we find that
acetate-CIMS spectra capture both functionalization (oxygen addition) and
fragmentation (carbon loss) as a function of OH exposure. The level of
fragmentation is observed to increase with increased oxidation. The predicted
condensed-phase secondary organic aerosol (SOA) average acid yields and O/C and H/C ratios
agree within uncertainties with previous chamber and flow reactor
measurements and ambient CIMS results. While acetate reagent ion chemistry is
used to selectively measure organic acids, in principle this method can be
applied to additional reagent ion chemistries depending on the application. |
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