AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Laboratory and Field Studies of Organic Aerosol Aging Using Nanospray-DESI High-Resolution Mass Spectrometry
ALEXANDER LASKIN, Julia Laskin, Peter Eckert, Tran Nguyen, Paula Lee, Katelyn Updyke, David Bones, Sergey Nizkorodov, Rachel O'Brain, Allen H. Goldstein, Pacific Northwest National Laboratory
Abstract Number: 618 Working Group: Aerosol Chemistry
Abstract Nanospray Desorption Electrospray Ionization (nano-DESI) is a recently developed ambient pressure surface ionization technique integrated with high resolution mass spectrometry (HR-MS) that enables molecular-level analysis of organic aerosol (OA) samples. The nano-DESI technique offers advantages of simplicity, ease of use, sensitivity, and signal stability, and eliminates the requirement for special sample preparation. OA deposited on common substrates are readily analyzed using this approach and provide high-quality HR-MS spectra using less than10 ng of analyte. In this presentation, we demonstrate the utility of the nano-DESI/HR-MS approach in a number of our recent studies focused on molecular identification of organic compounds in laboratory-generated and in field-collected OA samples reacted with gas-phase and particle-phase ammonia. We show that reactions of OA with ammonia yield highly conjugated nitrogen-containing species that have light-absorbing properties, and possibly contribute to the formation of “brown carbon”. Understanding of the OA composition at the molecular level allowed us to identify key aging reactions, including the transformation of carbonyls to imines, carbonyl-imine oligomerization, and intramolecular “four centered” carbonyl-imine cyclization that were detected in OA samples from both field and laboratory studies. Our results indicate that the reactions between carbonyl groups and ammonia play an important role in atmospheric aging of OA and contribute substantially to the formation of brown carbon in the atmosphere.