利用熱脫附氣相層析儀法量測工作環境空氣中氯甲烷與溴乙烯的方法研究

Measurement of Workplace Methyl Chloride and Vinyl Bromide Using Thermodesorption/Gas Chromatography

揮發性有機化合物氯甲院、澳乙偏屬於低沸點化合物，其沸點分別為_24.2C、16C，採樣時因 Tenax_TA、Tenax_GR、Carbopack B 無法提供足夠的安全採樣體積， 所以並不適用。多重床採樣管填充 125 毫克 Carbosieve SII、200 毫克 Carbopack B、200 毫克 Carbopack C，對於二個碳以上到三十個碳的揮發性有機化合物可提供足夠的 採樣體積。分析上，多重床採樣管在 250C、流量 30mLlmin 脫附 3 分鐘進入冷凍濃 縮儀，於_120C完全被捕捉住，然後再第二次熱脫附進入毛細管柱（CP_Sil 5 60m X 0.32mm ； 膜厚 5 mm），以火焰游離偵檢器（FID）進行定量定性分析。在二十八天 的保存期限之下，冷卻溫度 4C與冷凍溫度_30C並沒有分解的現象發生，所以建議採 樣管的保存須存放在密封罐內，並將密封罐儲存於 4C以下的冰箱。

Methyl chloride and vinyl bromide are both low boiling point volatile organic compounds. The boiling point of methyl chloride is _24.2C and the latter is 16C. A well-known problem is that it is difficult to obtain safety sampling volume by using the adsorbent of Tenax-TA, Tenax-GR, Carbopack B in field sampling. This study successfully demonstrated that multi-bed tubes consisting of Carbosieve SIII、Carbopack B、Carbopack C are capable of grasping enough sampling volume for C2 to C30 volatile organic compounds. In the experiment, with the condition of flow rate 30mL/min for 3 min at 250C, methyl chloride and vinyl bromide were first thermally desorbed from multi-bed tubes and then cryogenically focused by liquid nitrogen at _120 C, then finally carried into a 60 m long capillary column (CP-Sil 5 60m x 0.32mm ; Film thickness 5 um) for separation. The compounds were identified qualitatively and quantitatively by flame ionization detector (FID). Decomposition is negligible within 28 days at freezing temperature -30C and cooling temperature 4C. Hence, the better store condition is in a sealed jar, and were kept under cooling temperature of 4C in a refrigerator.