改进GC/FID法连续观测大气中CO浓度

An improved gas chromatography system for continuous measurement of atmospheric CO

改进装配有氢火焰离子化检测器(即FID)的气相色谱仪(GC),可连续监测大气中痕量气体CO浓度。本系统采用单阀双柱反吹进样技术,优选前置柱能更有效地剔除杂质,提高了分析柱效率,保持色谱基线平稳,提高分辨率和定量分析的准确率。优化后的气路设计与色谱柱的改进,使GC/FID对CO的最低检出限达到10×10-9、精密度误差小于2%,准确度在±2%之内。将气相色谱与动态气体稀释仪耦合使系统能够自动进行工作曲线校准,系统自动采样、分析和标定,无需人员职守。对北京大气CO连续观测结果表明,北京大气CO浓度变化受气象要素与排放源双重控制。

The improved gas chromatograph （GC） equipped with hydrogen flame ionization detector （FID） could measure trace gas CO in an air sample continuously. This system adopted single-valve, two-column and back-flushing injector techniques. The selective pre-column could get rid of impurities effectively, enhance analytical efficiency, keep baseline smoothly and improve resolution and the accuracy of quantitative analysis. The optimized gas line and improved column make the detection limit for CO reach 10 × 10^-9, and the precision is below 2% and accuracy in ＋2%. The system could calibrate working standard curves automatically by combi- ning GC with dynamic gas dilution system. It can sample, analyze and calibrate automatically without manual opertion. The continuous measurement of CO in Beijing showed that the concentrations of CO were controlled by both meteorological factors and surface emission sources.