AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Functional Group Distributions in Photolytically Generated Organic Aerosol
Alicia Kalafut-Pettibone, Joseph Klems, W. SEAN MCGIVERN, National Institute of Standards and Technology
Abstract Number: 465 Working Group: Aerosol Chemistry
Abstract Secondary organic aerosol (SOA) particles consist of complex mixtures of oxygenated organic compounds for which the identification and quantification of individual chemical species is intractable. However, knowledge of the nature of the oxygenated functional groups can provide valuable insight into the sources, oxidative aging, and cloud condensation nucleus propensity of collected particles. Toward this end, we have applied a recently developed high-performance liquid chromatography/ultraviolet-visible spectroscopy (HPLC/UV-VIS) methodology for determining functional group distributions through chemical derivatization to synthetic organic aerosol samples. Previously, our group has characterized three derivatization reagents that are specific to hydroxyl (OH), non-acid carbonyl (C=O), and carboxylic acid (COOH) moieties and enhance both ultraviolet absorption response and electrospray (ESI) ionizability for mass spectrometry. The functional group specificity and linearity of the ultraviolet response of these derivatization substituents allows the relative concentrations of the individual moieties to be determined. The enhanced ionizability, due to the presence of moderately basic nitrogen in the derivatization reagents, allows organic aerosol samples to be effectively studied using mass spectrometry, despite the often poor ESI ionizability of typical SOA constituents. In the present work, this derivatization methodology has been applied to extracts of filter-collected samples of particles derived from the 254 nm photodissociation of 1-iodooctane. The resulting product spectrum is complex, showing several chromatographically resolved peaks and a broad unresolved mixture. Triple-quadrupole mass spectrometry has been used to identify these individual compounds and the concentrations of the OH, C=O, and COOH moieties in the complex mixture. The products are derived from a single 1-octyl radical isomer, and these results will be used to constrain a model of the particle formation mechanism focusing on conversion of the octyl peroxy radicals to octoxy radicals and subsequent decomposition, isomerization, and termination by reaction with oxygen.