氯乙烯單體(Vinyl chloride monomer, VCM)是工業上生產聚氯乙烯 (Polyvinyl chloride, PVC)的單體，具肝毒性，屬毒性與致癌物，而1, 2-二氯乙烷(1, 2-dichloroethance, EDC)為製造氯乙烯之反應起始物。
氯乙烯與1, 2-二氯乙烷因蒸氣壓大，容易從製程設備元件如法蘭(flange)接合處，破損之密封墊片(gasket)、幫浦等元件中逸散或洩漏。然而，現今我國環保署環檢所所訂定之NIEA A715方法或美國環保署TO-15等檢測方法雖在分析物表單中包含此兩物質，但其方法為離線式(off-line)而非在線式(on-line)，是以採樣罐收集空氣後送入氣相層析儀質譜儀 (GC-MS)進行分析，其缺點是不易捕捉現場排放當下高值與濃度變化，故本研究結合了前濃縮熱脫附技術(thermal desorption; TD)並串聯GC-MS，鎖定氯乙烯與1, 2-二氯乙烷而開發了GC-MS在線監測方法，可獲得逐時濃度資料，有助於未來健康風險評估工作。
考量台灣空氣偏高的相對濕度、溫度會對於線上濃縮造成嚴重干擾而影響定量，故在本研究中對於TD單元開發一套除水模組，嘗試解決以往連續監測時高水氣帶來的困擾，並大幅降TD以及質譜儀受水氣干擾的影響。針對NIEA A715.15B中57種VOCs檢量線相對標準偏差值介於0.98~9.37%，其中氯乙烯檢量線RSD值為5.29%，多點校正相關係數R2在0.99以上，偵測極限0.024 ppb以下。在雲林六輕工業區附近橋頭國小許厝分校為期約十天的連續間測工作中(2016/11/10 – 11/20)出現的瞬間最高濃度為約1.28 ppb (v/v) (11/14日)，出現在風向由東北轉向西北的時間，而其餘大部分時間濃度皆低於0.2 ppbv。
本研究主要目的是建立空氣中VCM與EDC連續監測技術，使未來更能有效得知此兩物質在空氣中濃度變化與瞬間峯值，藉此了解特定工業對對周界空氣品質的影響，亦可作為工廠為求降低對環境、健康衝擊而自我管理或評估減排成效之依據。

Vinyl chloride is the monomer of polyvinyl chloride (PVC) and is commonly addressed as vinyl chloride monomer (VCM) in the relevant industries. VCM is both liver-toxic and carcinogenic, and with its precursor of 1, 2-dichloroethane (EDC), are produced in large amounts in Taiwan. For instance, the annual production of VCM is greater than 1.25 million tons from the top two producers.
Because of the high volatility of both VCM and EDC, fugitive emissions from leaky components of flanges, gaskets, pumps, pipelines, etc. are widespread. Monitoring of these two compounds of high toxicity in ambient air is essential to the health and safety of the general public and factory workers. Despite of the necessity in monitoring, the current analytical methods for these two compounds are off-line methods such as the U.S. TO-15 and NIEA 715 of Taiwan EPA. In these off-line methods, air samples are collected with canisters and analyzed by gas chromatography-mass spectrometry (GC-MS). The major drawback of these off-line GC-MS methods is the lack of capabilities to capture peak emissions for the exposure assessment of the worst-case-scenario. As a result, in this study, an on-line method by coupling the thermal desorption (TD) technique with GC-MS method was developed to perform unattended continuous monitoring of ambient VCM and EDC in the field.
To cope with the interferences brought upon by the high humidity in ambient air which often times led to ice clogging in the sorbent trap as well as high noise levels in MS detection, a water-removal stage prior to TD was developed with only a minor modification in the original TD configuration. The resulting TD-GC-MS method was tested to show precision in the range of 0.98 – 9.37% (RSD) for 57 compounds listed in NIEA 715. Of the 57 compounds, VCM showed a precision of 5.29%, linearity (R2) of 0.99 and method detection limit (MDL) of 0.024 ppb. In the field experiment during the period 2016/11/10 - 11/20，the maximum concentration of VCM was 1.28 ppb (v/v) occurred on Oct. 11, when the direction swept from northeast to northwest. For the rest of the measurement period, VCM concentration was either small (below 0.2 ppbv) or below the detection limit.

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