配备低压进样系统的GC-FID法测大气中的CO和CH_4

Determination of atmospheric CO and CH_4 by GC-FID equipped with a low-pressure injector

将自主研发的低压进样系统与GC-FID法相结合,解决了低压样气难以抽取进样的技术难题,实现了对SUMMA采样罐内低压样气中CO、CH4的分析.罐内样气压强大于30kPa情况下,该进样装置能将待测低压气体提升至常压状态并完成进样过程.本系统采用3个六通阀、5分子筛与TDX-01双柱实现O2、CO、CH4的有效分离.通过对5分子筛柱的反吹去除杂质组份,既保持基线平稳,又可缩短分析周期,提高效率.该分析系统CO、CH4的最低检出限分别为9.2×10-9、5.5×10-9.本分析系统与美国加州大学Irvine分校Donald R.Blake实验室针对CO、CH4比对的相对误差分别低3%和1%.

An improved GC-FID equipped with a self-designed low-pressure injector was developed for the determination of low-pressure CO and CH4 from the SUMMA canister.The self-designed injector can increase the sample pressure from lower to 30kPa in the canister to 100kPa effectively.The improved system could successfully separate O2,CO and CH4 with a combination of three 6-port valves,two columns（5 and TDX-01） and back-flushing techniques.The 5 packed column used as pre-column can remove impurities effectively,keep the baseline smooth and enhance analytical efficiency.The detection limit of the improved GC-FID method can reach 9.2 × 10-9 for CO and 5.5 × 10-9 for CH4.International inter-comparison between the laboratories of Peking University and University of California Irvine was conducted and the relative errors between the two laboratories for CO and CH4 were below 3% and 1%,respectively.