利用熱脫附/氣相層析儀法量測氣態四氯乙烯

Using Thermodesorption/Gas Chromatography for the Measurement of Volatile Tetrachloroethylene in the Air

以固體吸附劑Tenax-TA （60-80 mesh） 吸附空氣中氣態四氯乙烯，再經由加熱脫附後注入氣相層析儀分析的方法已建立。採樣袋中配製適當濃度氣態四氯乙烯標準品，以氣體針注入採樣管中，再放入熱脫附/冷凝濃縮儀中以240℃熱脫附6 分鐘，熱脫附的同時並經由液態氮冷凍（-70℃）將之濃縮於一微小空間中，再以1200 ℃/min的快速升溫注入氣相層析儀中分析。層析條件為：60℃恆溫，載體氣體氮氣的流速為6 mL/min，利用30 m× 0.53 mm ；1.5 μm 膜厚的DB-1 管柱分離。在27℃與相對濕度80 % 及100 ppm 濃度值條件下利用光游離偵檢器所量測四氯乙烯破出體積值為2.5Ｌ。四氯乙烯在常溫及4℃冷藏貯存28 天後其變化率在± 10 %之內。實驗室內比對以Tenax-TA 管與活性碳管各自抽取濃度50 ppm 相對濕度分別為0%與80%的四氯乙烯樣品各1.5Ｌ，再分別以熱脫附法與溶劑萃取法脫附後注入氣相層析儀分析，比對結果濃度值相對差異在12﹪以內且不受樣品中所含濕度影響。

A method for the measurement of volatile tetrachloroethylene in the air by thermodesorption / gas chromatography was established. Injecting suitable volume of tetrachloroethylene air sample prepared in the sampling bag into Tenax-TA tube, then thermally desorbed at 240℃ for 6 min while cryotrapped at -70℃ in order to concentrate the analyte in a tiny space before went into the capillary column (DB-1, 30 m× 0.53 mm; film thickness 1.5μm). Breakthrough volume of tetrachloroethylene was measured by photoionization detector in the condition of 27℃and 80 % relative humidity with twice of permissible exposure limits values (100 ppm), of 2.5 liters. The variance of stability was within ±10% when putting the sampling tubes in both at room and 4℃ temperature in a period of 28 storage days. In an intralaboratory comparison between the developed method and the current method, 1.5 liters of 50 ppm standard gas samples with two kinds of relative humility 0% and 80% were sucked into Tenax-TA and charcoal tubes, then desorbed by theramal or solvent extraction and injected into GC,respectively. Comparison result showed the percent difference was within 12﹪and independent with the humidity of the samples.