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| Titel |
Analysis of secondary organic aerosol using a Micro-Orifice Volatilization Impactor (MOVI) coupled to an ion trap mass spectrometer with atmospheric pressure chemical ionization (APCI-IT/MS) |
| VerfasserIn |
M. Brueggemann, A. Vogel, T. Hoffmann |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250066724
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| Zusammenfassung |
| We describe the development and characterization of a Micro-Orifice Volatilization Impactor
(MOVI) which is coupled to an ion trap mass spectrometer with atmospheric pressure
chemical ionization (APCI-IT/MS), and its application in laboratory and field measurements.
The MOVI-APCI-IT/MS allows the quantification of organic acids and other oxidation
products of volatile organic compounds (VOCs) in secondary organic aerosols (SOA) on a
semi-continuous basis. Furthermore, the vapor pressure and saturation concentration of the
particle components can be estimated.
The MOVI was first described in 2010 by Yatavelli and Thornton (Yatavelli and
Thornton, 2010). It is a single stage, multi-nozzle impactor with 100 nozzles, each having a
diameter of 150Â μm. At a flow-rate of 10Â L-
min-1 air is drawn through the MOVI and
particles are collected on a deposition plate. The cut-point diameter (d50, diameter
of 50% collection efficiency) is at 130Â nm. A low pressure-drop of only 5.3% of
atmospheric pressure behind the nozzles allows collecting not only low-volatile but even
semi-volatile compounds, which are an important part of SOA. After collecting particles
hydrocarbon-free synthetic air is led over the collection surface into the APCI-IT/MS and
the collection surface is heated up to 120Â Ë C in less than 200Â s, volatilizing the
sampled SOA. The vaporized compounds are transferred into the ion source and
subsequently analyzed by mass spectrometry. Due to the soft ionization at atmospheric
pressure the obtained mass spectra show only low fragmentations and can easily be
interpreted.
In laboratory experiments the MOVI-APCI-IT/MS was used for the chemical analysis of
SOA generated from α-pinene-ozonolysis in a smog chamber. The limit of detection was
found at 7.3 ng for pinic acid. The vapor pressure log p0 and the saturation concentration
C25* for pinic acid were calculated from the desorption temperature using the method
presented by Faulhaber et al. (Faulhaber et al., 2009). Furthermore, in summer 2011
the MOVI-APCI-IT/MS was successfully tested in field measurements during the
„Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics and
Nitrogen – Rocky Mountain Biogenic Aerosol Study” (BEACHON-RoMBAS) in a
ponderosa pine woodland in the southern Rocky Mountains of North America. The study was
focused on understanding the formation, growth and properties of biogenic organic
aerosol. We measured the composition of the aerosol particles and determined the
concentration of pinic acid and isobaric substances. By means of intercomparison
studies with other instruments like an aerosol mass spectrometer (AMS) and a MOVI
coupled to a chemical ionization mass spectrometer (CIMS) we could validate our
measurements.
References:
Faulhaber, A. E., Thomas, B. M., Jimenez, J. L., Jayne, J. T., Worsnop, D. R., Ziemann, P.
J., Atmos. Meas. Tech., 2009, 2, 15–31.
Yatavelli, R. L. N. and Thornton, J. A., Aerosol Sci. Technol., 2010, 44, 61–74. |
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