Quartz filter-based thermal desorption gas chromatography mass spectrometry for in-situ molecular level measurement of ambient organic aerosols.

Thermal desorption aerosol gas chromatography (TAG) is an effective technique for online chemical characterization of organics in atmospheric fine particulate matter (PM2.5) on the molecular level. Unlike the previously reported impactor- or metal filter-based TAG, in this study, a replaceable quartz filter-based TAG (Q-TAG) was developed to achieve online measurement of organic constituents in ambient PM2.5. A homemade device for automatic online sampling and pretreatment of aerosols was developed and coupled with gas chromatography-mass spectrometry (GC-MS) by a 4-port valve. Performance of the Q-TAG system was evaluated using C7 - C40 n-alkanes to cover a wide range of volatility. C11 - C40 could be measured by Q-TAG. The response of their peaks depends on their volatility and thermal desorption conditions (the desorption time and the flow rate). Under the optimized conditions, good precision (<12%), acceptable linearity (R2> 0.98) and high sensitivity (detection limits from 0.02 to 0.01 ng) of C13 - C40 were obtained. The developed Q-TAG system was applied for online analysis of organic species in ambient PM2.5. The Q-TAG is suitable for detection of semi and low volatile organic species in particulate matter, and its filter can be easily changed, making it a useful tool in molecular characterization of ambient organic aerosols.