Integrated gas chromatography for ultrafast analysis of volatile organic compounds in air

An integrated instrumentation of a cryogenic microtrap-thermal desorption-low thermal mass (LTM) fast gas chromatographic (GC) system had been designed and evaluated for the ultrafast enrichment and separation of trace amounts of highly volatile organic compounds (VOCs) in air. The LTM fast GC column was wrapped uniformly on outer surface of a thin metal heating cylinder of 65mm O.D. and 0.5mm in thickness. Both of microtrap and LTM column could be rapidly cooled by liquid CO2 down to -35°C, and heated by resistive heating. A 10m×100µm i.d. micro-bore capillary column was used in the LTM GC column module to provide a high separation speed. Key operational parameters, including adsorbent mass, trapping temperature, thermal desorption temperature and injection time were optimized. Under the optimized condition, the 39 species of TO-14 VOCs were well resolved and quantified in less than 3min. The detection limits were in the range of 8 ppt-0.22 ppb at sampling volume of 50mL and trapping temperature of -10°C. The average peak width was 0.9s, and the peak capacity of ~150 (at unit resolution) was obtained. The applicability of the setup was evaluated by analyzing three real environmental samples, where some typical VOCs at sub ppb level were detected.