美國聯邦政府頒布《清淨空氣法》〈Clean Air Act Amendments, CAAA〉定義有害空氣污染物 (Hazardous Air Pollutants, HAPs) 為任何會引起或導致死亡率增加，嚴重危害人體健康且不可恢復，或造成喪失能力但能恢復之徵狀，如：生殖影響、生理缺陷、不良環境及生態影響等。 國際間現行HAPs分析方法是U.S. EPA TO-15，臺灣環保署也開發了類似方法NIEA A715.16B。使用採樣罐收集空氣樣品，再帶回實驗室以氣相層析質譜儀進行分析。空氣污染防制法第二章第15條規定，應每六天於特殊性工業區佈點採樣，每次連續採集24小時，但此方式所獲得之數據並無法反映工廠排放HAPs的瞬間變化，容易錯失高值事件。 為了調查工業區中HAPs，於正確的時機捕捉高值，本研究開發一套熱脫附氣相層析質譜儀在線分析方法，能獲得86種揮發性有機化合物每小時連續濃度值。經品保品管測試，檢量線%RSD為1.2~19.3%，R2為0.995~1.000，準確度回收率為89.3~114.8%，精確度%RSD為0.6~19.1%，方法偵測極限為0.04~1.41 ppb。 依據過去經驗，儀器24小時不停地運轉，離子源在3天的時間內感度下降高達80%。為了改善離子源快速耗損的問題，本研究發現離子源拉出極板 (Drawout plate) 孔徑尺寸將會影響質譜儀的穩定性及數據的品質。在離子源中Drawout plate為一離子通道，本身不帶電，會與Repeller形成電壓差，將離子拉引至後端。 2020年8月至11月於北部某工業區進行實場監測，相較於3和9 mm Drawout plate，使用6 mm Drawout plate能延長離子源壽命，有效拉長監測時間，最長可達14天，查核回收率介於69.1~131.2%，減少維護保養的頻率，提高實場監測的數據有效率。 連續監測數據同時和Canister和PTR-MS進行平行比對，證實Online TD-GC-MS對於微量空氣污染物的判定非常準確，具備足夠的靈敏度，以每小時逐時數據捕捉高值，是一種可靠的線上連續方法監測環境中HAPs。;The 1990 Clean Air Act Amendments (CAAA) of the United States defines Hazardous air pollutants (HAPs), which are those known to cause cancer and other serious health impacts. Currently the most pouplar analytical method for ambient volatile organic HAPs is U.S. EPA TO-15 worldwide. A similar method called NIEA A715.16B was also developed by Taiwan EPA. Both methods use surface treated stainless canisters to collect air samples, followed by gas chromatography mass spectrometry (GC/MS) analysis. According to Taiwan EPA regulations for special industrial areas, canister samples are collected every six days at specific locations. However, the dataset of such a poor temperal resolution cannot truly reflect the instantaneous changes in HAPs emissions from relevant industries. In order to capture peak values of the target HAPs in industrial zones at the right moments for source investigation, this research developed an online thermal desorption (TD) coupled GC/MS method to obtain hourly concentrations of selected 86 HAPs at sub-ppb level. From past experience, it is known that when the TD-GC/MS instrument runs constantly, the ion source could degrade rapidly by as much as 80% in sensitivity in 3 days. In order to cope with the problem, we found that the size of the drawout plate in the ion source affects the stability of MS and thus data quality over time. The drawplate is an ion channel gate which forms a voltage gradience with the repeller, guiding ions to the back end. The field monitoring was carried out in an industrial area from August to November 2020. By comparing with two different sized drawout plates of 3 and 9 mm, the 6 mm drawout plate can effectively prolong the monitoring time period by extending the life of the ion source to up to 14 days and; hence, significantly reduces the downtime and improves the working efficiency of field monitoring. The continuous monitoring data was compared in parallel with both canisters and PTR-MS. The online TD-GC-MS system is very accurate and sensitive in determining air pollutants at trace levels, and is able to capture high values with hourly resolution. It has been proven to be a credible on-line method to monitor ambient volatile organic HAPs.
