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| Titel |
Online atmospheric pressure chemical ionization ion trap mass spectrometry (APCI-IT-MSn) for measuring organic acids in concentrated bulk aerosol – a laboratory and field study |
| VerfasserIn |
A. L. Vogel, M. Äijälä, M. Brüggemann, M. Ehn, H. Junninen, T. Petäjä, D. R. Worsnop, M. Kulmala  , J. Williams, T. Hoffmann |
| 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 ; 6, no. 2 ; Nr. 6, no. 2 (2013-02-20), S.431-443 |
| Datensatznummer |
250017400
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| Publikation (Nr.) |
 copernicus.org/amt-6-431-2013.pdf |
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| Zusammenfassung |
| The field application of an aerosol concentrator in conjunction with an
atmospheric pressure chemical ionization ion trap mass spectrometer
(APCI-IT-MS) at the boreal forest station SMEAR II at Hyytiälä,
Finland, is demonstrated in this study. APCI is a soft-ionization technique
allowing online measurements of organic acids in the gas and particle phase.
The detection limit for the acid species in the particle phase was improved
by a factor of 7.5 to 11 (e.g. ∼40 ng m3 for
pinonic acid) by using the miniature versatile aerosol concentration
enrichment system (mVACES) upstream of the mass spectrometer. The APCI-IT-MS
was calibrated in the negative ion mode with two biogenic organic acid
standards – pinic acid and pinonic acid. Pinic acid was used as a surrogate
for the quantification of the total amount of organic acids in the ambient
aerosol based on the total signal intensities in the negative ion mode. The
results were compared with the total organic signal of a C-ToF-AMS during
the HUMPPA-COPEC 2010 field campaign. The campaign average contribution of
organic acids measured by APCI-IT-MS to the total submicron organic
aerosol mass was estimated to be about 60%, based on the response of
pinic acid. Very good correlation between APCI-IT-MS and C-ToF-AMS
(Pearson's R = 0.94) demonstrates soft-ionization mass
spectrometry as a complimentary technique to AMS with electron impact
ionization. MS2 studies of specific m/z ratios recorded during
the HUMPPA-COPEC 2010 field campaign were compared to MS2
studies of selected monoterpene oxidation products formed in simulation
chamber experiments. The comparison of the resulting fragments shows that
oxidation products of the main VOCs emitted at Hyytiälä (α-pinene
and Δ3-carene) cannot account for all of the
measured fragments. Possible explanations for those unaccounted fragments
are the presence of unidentified or underestimated biogenic SOA precursors,
or that different products are formed by a different oxidant mixture of the
ambient air compared to the chamber ozonolysis. |
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