Optimization of a thermal desorption-gas chromatography/mass spectrometry method for characterization of semi-volatile organic compounds in high time resolved PM2.5

Özet

Organic aerosol (OA) is an important fraction of fine particulate matter. Most primary OA emissions comprisesemivolatile organic compounds (SVOCs) that are reactive and may partition into particle and vapor phases.Collection of SVOCs in the particle phase at high time resolution reduces positive and negative artifacts, butrequires sensitive analytical techniques for chemical characterization. In this work, we investigated the effect ofthermal desorption-gas chromatography/mass spectrometry (TD-GC-MS) analytical variables on 16 polycyclicaromatic hydrocarbons (PAHs) and 29 n-alkanes. Analytical responses of target compounds were mostly influenced by trap desorption time and GC column pressure. The optimal TD-GC-MS trap desorption conditions were350 °C for 10 min at GC constant pressure mode of 17 psi. Good linearity (R2 > 0.99) was observed for all targetanalytes (with the exception of 6 ring PAHs and C35–C39 n-alkanes). Method detection limits were0.038–0.157 ng m−3 and 0.028–0.355 ng m−3 for PAHs and n-alkanes, respectively. The optimized method wastested on PM2.5 samples collected with the high-volume sampling technique at high temporal resolution of 2 h.Analysis of a sample, followed by analysis of a blank, did not show carryover. The optimized TD-GC-MS methodshowed the capability to resolve diurnal variations of target analytes in high time resolved PM2.5. Using TD-GCMS for analysis of high time resolved PM2.5 will contribute to the improvement of source apportionment,emission inventories, and global chemistry-climate models.