AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Functional Group Distributions in Photolytically Generated Organic Aerosols
Alicia Kalafut-Pettibone, W. SEAN MCGIVERN, National Institute of Standards and Technology
Abstract Number: 518 Working Group: Aerosol Chemistry
Abstract The gas-liquid partitioning of oxidized volatile organic carbon (VOC) is strongly dependent on the composition of the oxidation products and can be correlated to the distribution of oxygenated moieties present in these products. A liquid chromatography/tandem mass spectrometry (LC/MS-MS) methodology is described to probe this distribution in organic aerosol particles. In this study, we present the distribution of carbonyls (aldehydes and ketones), hydroxyls, and carboxylic acids present in particles derived from the oxidation of octyl radicals that are formed from iodooctane photolysis. A flow cell apparatus utilizing uncoated fluorescent lights (254 nm mercury line sources) for photolysis is used as a reactor with concentrations that yield rapid oxidation in a NO$_x-free environment. A series of chemical derivatization steps on samples extracted from filtration of the flow cell output provides significant information about the presence of oxygenated functionalities on the observed products. Additionally, the iodooctane photolysis yields a broad range of recombination products with relatively low oxygen content relative to their masses, consistent with waxy, hydrophobic oligomers. The measured distributions are then used to constrain a permutation model of the oxidation that can effectively predict the major condensed-phase products and yields by assuming different contributions to the predicted vapor pressures from the observed oxygenated functionalities.