气相色谱法检测大气中N2O浓度

由于受大气中Ｏ２、Ｈ２Ｏ和氯氟烃的干扰，大气中的Ｎ２Ｏ难于用简单的气相色谱法连续观测。实验中对带有电子捕获检测器的气相色谱仪（Ｇ－ＥＣＤ）进行了改进，系统中安装了１０通进样反吹阀和４通切换阀，色谱系统中同时采用两根ＰｏｒａＰａｋＱ填充柱，并在进样系统中安装了水蒸汽和ＣＯ２过滤吸收器。这样，干扰物不进入检测器，对Ｎ２Ｏ信号没有干扰，从而提高了Ｎ２Ｏ分析灵敏度和精确度。从１９９２年１１月起，我们开始对北京大气Ｎ２Ｏ浓度进行长期定位测检。用这种方法测得的北京大气Ｎ２Ｏ月平均浓度介于３０１±９．８ｐｐｂｖ至３３５±２２．５ｐｐｂｖ之间，平均值为３１７±１２．８ｐｐｂｖ。

Analysis of Atmospheric Nitrous Oxide with a Modified GC System

It is very difficult to analyze atmospheric nitrous oxied with common gas chromatograph (GC) because of its low concentration and the interference of O₂, H₂O and chloro-Fluoro-hydrocarbons. Therefore, a GC equipped with an electron capture detector (ECD) was modified for N₂O measurement. A 10-port valve for sampling and back flushing as well as a 4-port switching valve was incorporated into the GC System while a precoloum was used in combination with an analytical column. In addition, two absorbent traps were equipped in the inlet system to filter off H₂O and CO₂. In the proiect caried out in Beijing, China since November 1992 to monitor atmospheric nitrous oxide, the concentration of atmospheric N₂O in Beijing was analyaed with this modified system to be 317±12.8 ppbv.