Comparison of Solvent Extraction and Thermal-Optical Carbon Analysis Methods: Application to Diesel Vehicle Exhaust Aerosol

Filter samples of particulate emissions from two diesel automobiles were analyzed by solvent extraction with a hot toluene/1-propanol mixture, by thermal-optical carbon analysis, and by X-ray fluorescence analysis. On the average, carbon accounted for 83% of the particulate matter, and organic carbon comprised 70% of the extractable mass. The ratio of elemental carbon as measured by the thermal-optical technique to unextractable mass was 1.05 ± 0.04. For most of the filters the unextractable mass was predominantly elemental carbon. However, for the filters with the largest amounts of unextracted material the elements Fe, S, Al, Si, and Ca were present in significant amounts (0.3-5% each of the unextractable mass when expressed as oxides).