Articles | Volume 8, issue 12
Atmos. Meas. Tech., 8, 5177–5187, 2015
Atmos. Meas. Tech., 8, 5177–5187, 2015

Research article 10 Dec 2015

Research article | 10 Dec 2015

Comparison of advanced offline and in situ techniques of organic aerosol composition measurement during the CalNex campaign

J. Timkovsky1, A. W. H. Chan2,a, T. Dorst1, A. H. Goldstein2,3, B. Oyama1,4, and R. Holzinger1 J. Timkovsky et al.
  • 1Institute for Marine and Atmospheric Research Utrecht, Utrecht University, PO box 80005, 3508 TA, the Netherlands
  • 2Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, USA
  • 3Department of Civil and Environmental Engineering, University of California, Berkeley, California, USA
  • 4Department of Meteorology, Institute of Astronomy, Geophysics, and Atmospheric Sciences, University of São Paulo, Brazil
  • anow at: Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario, Canada

Abstract. Our understanding of formation processes, physical properties, and climate/health effects of organic aerosols is still limited in part due to limited knowledge of organic aerosol composition. We present speciated measurements of organic aerosol composition by two methods: in situ thermal-desorption proton-transfer-reaction mass spectrometry (TD-PTR-MS) and offline two-dimensional gas chromatography with a time-of-flight mass spectrometer (GC × GC/TOF-MS). Using the GC × GC/TOF-MS 153 compounds were identified, 123 of which were matched with 64 ions observed by the TD-PTR-MS. A reasonable overall correlation of 0.67 (r2) was found between the total matched TD-PTR-MS signal (sum of 64 ions) and the total matched GC × GC/TOF-MS signal (sum of 123 compounds) for the Los Angeles area. A reasonable quantitative agreement between the two methods was observed for most individual compounds with concentrations which were detected at levels above 2 ng m−3 using the GC × GC/TOF-MS. The analysis of monocarboxylic acids standards with TD-PTR-MS showed that alkanoic acids with molecular masses below 290 amu are detected well (recovery fractions above 60 %). However, the concentrations of these acids were consistently higher on quartz filters (quantified offline by GC × GC/TOF-MS) than those suggested by in situ TD-PTR-MS measurements, which is consistent with the semivolatile nature of the acids and corresponding positive filter sampling artifacts.