Comprehensive two-dimensional gas chromatography mass spectrometry with a solid-state thermal modulator for in-situ speciated measurement of organic aerosols

Abstract

Thermal desorption aerosol gas chromatography mass spectrometry is capable of online measuring speciated organics in atmospheric aerosols. Compared to the one-dimensional gas chromatography, comprehensive two-dimensional gas chromatography increases the resolution and the sensitivity, mitigates the unresolved complex mixture and co-elution occurred in one-dimensional gas chromatography. In this study, we report a quartz filter-based thermal desorption aerosol comprehensive two-dimensional gas chromatography mass spectrometry (2D-Q-TAG). It combines a solid-state thermal modulator with a quartz filter-based thermal desorption aerosol gas chromatography mass spectrometry. The solid-state thermal modulator conducts modulation independently from the chromatographic oven without using cryogens or compressed air, which makes the system readily adaptive for field measurement. The 2D-Q-TAG was evaluated using C7-C40 n-alkanes and 16 polycyclic aromatic hydrocarbons (PAHs). It has low limits of detection from 0.001 to 0.104 ng. The instrument was then deployed to measure atmospheric PM2.5 (particulate matter with an equivalent aerodynamic diameter ≤ 2.5 μm) in urban Beijing. It allows in-situ detection of speciated organics in atmospheric aerosols with hourly time resolution. Organic classes including alkanes, furanones, alcohols, aldehydes, ketones, acids, PAHs, oxy-PAHs, and alkyl-naphthalenes were well separated and detected. The total mass concentration of n-alkanes ranged from 122.1 to 629.9 ng/m3. Diurnal variation of n-alkanes was captured due to the high time resolution of the instrument.