[Analysis of Non-polar Organic Compounds in PM_2.5 by Rapid Thermo-desorption Method Coupled with GC/MS]

Non-polar organic compounds (NPOCs) associated with PM_2.5 in the atmosphere were analyzed by automated thermo-desorption (TD) coupled with gas chromatography/mass spectrometry (TD-GC/MS). The analyses for a total of 72 NPOCs were reviewed, including 34 PAHs, one Debenzothiophene, 27 alkanes (C₁₀-C₃₄), 5 hopanes and 5 steranes. Through this improved TD method, operation of filter loadings, TD condition and sample introduction were optimized. The MDL were 0.01-1.0, 0.1-8.0 and 0.50-2.0 ng·m^-3 for PAHs, alkanes, hopanes and steranes, respectively. Calibration curve linearities were above 0.9 for all compounds. The TD efficiencies were 95%-100% for PAHs, 81%-100% for alkanes and 83.1%-100% for hopanes and steranes. PM_2.5 samples were pretreated by TD and ultrasonic extraction methods separately and analyzed by GC/MS in two laboratories. Results from these two methods were comparable, as the relative biases were less than 30% for most compounds. Analysis results of PM_2.5 samples from Linan and Shanghai showed that NPOCs were higher in winter than that in summer. Alkanes were predominant among NPOCs, followed by PAHs. Source analysis by PAH characteristic ratios indicated that fossil fuel burning and coal burning were the main sources of NPOCs in the two sites during the sampling periods.