New Sensitive and Quantitative Analysis Method for Organic Nitrogen Compounds in Urban Aerosol Samples

Abstract

Atmospheric aerosols contain a highly complex mixture of organic and inorganic compounds; however, as a chemical class relatively little is known about organic nitrogen (ON) content, with few satisfactory methods for speciated analysis. In this paper we report a sensitive and quantitative method for the speciation of ON within ambient atmospheric aerosol. Aerosol samples, collected on quartz microfiber filters, were extracted in water followed by solid phase extraction, elution, and concentration before analysis by comprehensive gas chromatography with a nitrogen chemiluminescence detection system (GCxGC-NCD). The NCD detection method was optimized using liquid standards. The GCxGC-NCD method showed high selectivity, sensitivity, and equimolarity in its response to individual organic compounds. Limits of detection (LOD) and limits of quantitation (LOQ) for four ON standards (1-nitropentane, o-toluidine, nonanenitrile, and quinoline) were determined to be in the range 0.16-0.27 pgN and 0.71-1.19 pgN, respectively. Between 21 and 57 different ON compounds were found in urban aerosol, (including 10 nitriles, 9 alkyl nitro compounds, 4 nitro-phenols, 4 amides, 3 nitrosamines, and 2 nitro-PAHs) on different dates from a city center location. Pyrrole (8.26-39.21 ngN m(-3) air) and N-butyl-benzenesulfonamide (6.23-20.87 ngN m(-3) air) were the most abundant ON compounds observed in all samples analyzed. The average mass loading of the total identified ON was 532.51 ngON m(-3) air. The sensitivity, selectivity, and relative ease of quantitation of unknown ON components makes the technique a significant improvement over previous laboratory methods.