Impacts of Aerosol Aging on Laser Desorption/Ionization in Single-Particle Mass Spectrometers |
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| Authors: | Lindsay E. Hatch Kerri A. Pratt J. Alex Huffman Jose L. Jimenez |
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| Affiliation: | 1. University of California, San Diego, La Jolla, California, USA;2. Cooperative Institute for Research in Environmental Sciences, Boulder, Colorado, USA;3. Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado, USA |
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| Abstract: | Single-particle mass spectrometry (SPMS) has been widely used for characterizing the chemical mixing state of ambient aerosol particles. However, processes occurring during particle ablation and ionization can influence the mass spectra produced by these instruments. These effects remain poorly characterized for complex atmospheric particles. During the 2005 Study of Organic Aerosols in Riverside (SOAR), a thermodenuder was used to evaporate the more volatile aerosol species in sequential temperature steps up to 230°C; the residual aerosol particles were sampled by an aerosol mass spectrometer (AMS) and a single-particle aerosol time-of-flight mass spectrometer (ATOFMS). Removal of the secondary species (e.g., ammonium nitrate/sulfate) through heating permitted assessment of the change in ionization patterns as the composition changed for a given particle type. It was observed that a coating of secondary species can reduce the ionization efficiency by changing the degree of laser absorption or particle ablation, which significantly impacted the measured ion peak areas. Nonvolatile aerosol components were used as pseudo-internal standards (or “reference components”) to correct for this LDI effect. Such corrected ATOFMS ion peak areas correlated well with the AMS measurements of the same species up to 142°C. This work demonstrates the potential to accurately relate SPMS peak areas to the mass of specific aerosol components. Copyright 2014 American Association for Aerosol Research |
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