| 摘要: | 由於溫室效應氣體之濃度在大氣中逐年上升，其中二氧化碳、甲烷、氧化亞氮因具有較高濃度、長生命期與在紅外光區有高吸收之緣故；因此，本實驗之目的為建立自動化搭配逆吹系統以期能快速地分析上述三者溫室效應物種，實驗中所使用之管柱為Hayesep Q與Porapak Q。火焰離子偵測器負責二氧化碳與甲烷之量測，電子捕捉偵測器則負責氧化亞氮之量測；二氧化碳則在375 ̊C之條件下，經由使用鎳觸媒之甲烷轉化氣轉化為甲烷才可被火焰離子偵測器所量測。樣品迴圈約為2毫升，進樣壓力則設定為700 torr。二氧化碳、甲烷與氧化亞氮之線性關係分別為1.000、0.9907與0.9990；偵測下限則分別為1.02 ppmv、1.07 ppmv與6.40 ppbv。三種氣體在系統的量測下, 相對標準偏差 (Relative Standard Deviation) 皆在1%以內, 表現出實驗的精確性。The so called enhanced global warming is caused by the increase in the concentration of greenhouse gases (GHGs) in the atmosphere due to anthropogenic activities. Of all the GHGs, CO2, CH4, and N2O are the major contributors due to their large abundance, long lifetimes, and relatively strong IR absorption abilities. In this experiment, the three GHGs in the atmosphere will be measured using gas chromatography (GC) with the packed column back-flushed method. The stationary phases used for the packed columns are Hayesep Q and Porapak Q. For CO2 and CH4 analysis flame ionization detection (FID) is used, and for N2O analysis electron capture detection (ECD) is used. CO2 was first reduced into CH4 by an in-line Ni catalyst kept at 375 ̊C before detection with FID. To perform sample injection, the pressure for the sample loop (2 mL) was set at 700 torr with a pressure gauge which allowed automatic sample filling. The linearity for CH4, CO2, and N2O, as depicted by the correlation coefficients (R2), are 0.9907, 1.000, and 0.9990, respectively. Limits detection for these three gases are 1.07 ppmv, 1.02 ppmv, 6.40 ppbv, respectively. Precision, as depicted by the standard deviation (RSD), is better than 1% for the three gases. |
