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www.atmos-meas-tech-discuss.net/3/2013/2010/
doi:10.5194/amtd-3-2013-2010
© Author(s) 2010. This work is distributed
under the Creative Commons Attribution 3.0 License.
Near-infrared laser desorption/ionization aerosol mass spectrometry for measuring organic aerosol at atmospherically relevant aerosol mass loadings
Department of Chemistry, University of Vermont, Burlington, VT 05405, USA
Abstract. 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 aluminium probe and 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 SOA fluxes and to aid in remediating the discrepancy between modeled and observed atmospheric total SOA production rates and concentrations.
Discussion Paper (PDF, 1650 KB) Interactive Discussion (Closed, 4 Comments) Final Revised Paper (AMT)
Notice on Discussion StatusCitation: Geddes, S., Nichols, B., Todd, K., Zahardis, J., and Petrucci, G. A.: Near-infrared laser desorption/ionization aerosol mass spectrometry for measuring organic aerosol at atmospherically relevant aerosol mass loadings, Atmos. Meas. Tech. Discuss., 3, 2013-2033, doi:10.5194/amtd-3-2013-2010, 2010. Bibtex EndNote Reference Manager XML
