AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Comprehensive Characterization of Particulate Matter Using Sequential Thermal Extraction/Pyrolysis with On-line Gas Chromatography/Mass Spectrometry
Josef Beranek, Allison Coffman, Evguenii Kozliak, ALENA KUBATOVA, University of North Dakota
Abstract Number: 354 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract High-molecular weight (HMW) species may represent a significant portion of unidentified total organic matter in air particulate matter (PM). In order to recognize and characterize HMW species in PM and to determine its contribution to total organic carbon (OC), we developed and optimized a novel analytical method. The method is based on a stepwise (with 100 degreeC increments) thermal extraction (TE) performed up to 300 degreeC followed by stepwise pyrolysis (Py) at 400–800 degreeC with on-line gas chromatography/mass spectrometry (GC/MS). To prevent ambiguities in the assignment of evolving low molecular weight (LMW) compounds to pyrolyzed HMW species, it was important to remove (i.e., vaporize) all volatile LMW compounds using a combination of solvent extraction and TE (at 200 and 300 degreeC) prior to the pyrolysis. In addition, the complete vaporization of LMW OM was hindered by the analyte-matrix interactions in bulk wood smoke and urban PM when the procedure was conducted without the prior solvent extraction.
The developed method yielded specific thermal signatures/patterns of eluting organic species for two PM samples of different origin. The HMW constituents identified in pyrolyzed fractions (400–800 degreeC) were attributed to 1) pyrolysis products of unburned lignin residues in wood smoke PM, and to 2) biopolymers and large non-volatile hydrocarbons in urban PM. A significant contribution of HMW species was also observed in the aqueous extracts of wood smoke PM.
Apart from the ability to characterize HMW species in PM, sequential TE/Py-GC/MS has potential to improve the understanding of traditional thermal optical analysis for organic and elemental carbon by enabling a direct MS detection of thermally evolved species.