High-Precision GC-MS Analysis of Atmospheric Polycyclic Aromatic Hydrocarbons (PAHs) and Isomer Ratios from Biomass Burning Emissions

This manuscript describes an analytical method for the quantitative determination of 16-polycyclic aromatic hydrocar-bons (PAHs) using accelerated solvent extraction (ASE), followed by purification on a silica cartridge, and subsequent measurement by gas chromatograph coupled to a mass spectrometer (GC-MS). The solvent extraction parameters (T = 100 ˚C, P = 1500 psi, t = 30 min, V = 30 ml) are optimized with dichloromethane (DCM) in order to avoid fractiona-tion effect, thereby achieving quantitative mass recovery of PAHs. The purification of PAHs on silica cartridge elimi-nates the matrix effect, facilitates their enrichment from extracted solution and quantitative determination in presence of an internal-standard (Pyrene-D10). The analytical protocol has been successfully used for the quantification of 16-PAHs and their isomer ratios in atmospheric aerosols collected from northern India dominated by agricultural-waste (post-harvest paddy and wheat residue) burning emissions. Based on the analysis of ambient aerosols, collected from different sites, the overall recovery efficiency for 2- to 3-ring PAHs is 85 % and near 100 % recovery for 4- to 6-ring compounds