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| Titel |
Near-infrared laser desorption/ionization aerosol mass spectrometry for measuring organic aerosol at atmospherically relevant aerosol mass loadings |
| VerfasserIn |
S. Geddes, B. Nichols, K. Todd, J. Zahardis, G. A. Petrucci |
| 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 ; 3, no. 4 ; Nr. 3, no. 4 (2010-08-31), S.1175-1183 |
| Datensatznummer |
250001228
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| Publikation (Nr.) |
 copernicus.org/amt-3-1175-2010.pdf |
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| Zusammenfassung |
| A new method, near-infrared laser desorption/ionization
aerosol mass spectrometry (NIR-LDI-AMS), is described for the real time
analysis of organic aerosols at atmospherically relevant total mass
loadings. Particles are sampled with an aerodynamic lens onto an aluminum
probe. A moderate energy NIR laser pulse at 1064 nm is directed onto the
probe to vaporize and ionize particle components. Delayed pulse extraction
is then used to sample the ions into a reflectron time of flight mass
spectrometer for chemical analysis. The soft ionization afforded by the NIR
photons results in minimal fragmentation (loss of a hydrogen atom) producing
intact pseudo-molecular anions at [M-H]−. The limit of detection
measured for pure oleic acid particles (geometric mean diameter and standard
deviation of 180 nm and 1.3, respectively) was 140 fg (or 1.7 ng m−3 per
minute sampling time). As an example of the utility of NIR-LDI-AMS to
measurements of atmospheric importance, the method was applied to laboratory
chamber measurements of the secondary organic aerosol formation from
ozonolysis of α-pinene. High quality mass spectra were recorded with a 2-min
time resolution for total aerosol mass loadings ranging from 1.5 to
8.7 μg m−3. These results demonstrate the potential of NIR-LDI-AMS to allow
for more accurate measurements of the organic fraction of atmospheric
particulate at realistic mass loadings. Measurements at ambient-levels of
SOA mass loading are important to improve parameterizations of chamber-based
SOA formation for modeling regional and global SOA fluxes and to aid in
remediating the discrepancy between modeled and observed atmospheric total
SOA production rates and concentrations. |
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