双通道气相色谱法观测本底大气中的CH_4、CO、N_2O和SF_6

Dual channel GC system for measuring background atmospheric CH_4,CO,N_2O and SF_6

在商用Agilent6890N气相色谱仪基础上,通过自组装、集成及调试,在青海瓦里关全球大气本底站建立了双通道气相色谱在线观测系统,以实现同时高精度分析本底大气中的CH4、CO、N2O和SF6.同时,利用保留时间定性,用峰高定量CH4、CO和SF6,用峰面积定量N2O,对体积分数分别为2000.3×10-9、199.8×10-9、320.04×10-9和5.9×10-12的CH4、CO、N2O和SF6混合标气重复进样110次,分析时每隔3个未知样品穿插分析1个标气,以保证分析结果的可靠性.该站试运行期间的数据表明,该系统分析CH4、CO和SF6的稳定性较好,能满足清洁本底大气高精度、高准确度分析要求,分析结果的相对标准偏差(RSD)分别为0.04%、0.50%、0.08%和1.80%.

A high-precision dual channel GC system was set up at Mt. Waliguan Global Atmosphere Watch Station, and used to measure atmospheric CH4, CO, N2O and SF6. The gases were identified by retention time on an Agilent 6890N gas chromatograph. The concentrations of CH4, CO, SF6 were calculated from peak height and N2O from peak area. The RSD （Relative Standard Deviation） of 110 repeated injections were better than 0.04% for CH4 （2000.3×10^-9）, 0.5% for CO （199.8×10^-9）, 0.08% for N2O （320.04×10^-9） and 1.80% for SF6 （5.9×10^-12）. To meet the needs of high precision in-situ measurement, one standard gas injection was applied after every three unknown samples. Results from test operation showed that the system was suitable for background atmospheric CH4, CO and SF6 measurement with high precision, stability and reliability.