| Abstract: | 有害空氣污染物 (Hazardous Air Pollutants, HAPs) 又稱為空氣毒
性物質 (Air toxics)，因與民眾健康影響有關，近年來已成為備受關注
的焦點和議題。本研究以有害空氣污染物中之揮發性有機物為監測目標物種，稱為Toxic VOCs。現行我國針對HAPs之量測方法為不鏽鋼採樣罐搭配氣相層析質譜儀 (離線分析法)，因不能即時得知監測結果，且無法有效反映排放源的逐時排放特性，因此本研究將延續並加強實驗室所開發的線上連續監測方法，採用熱脫附氣相層析質譜儀 (Thermal Desorption Gas Chromatography/Mass Spectrometry, TD- GC/MS) 與除水設備，可監測86種揮發性有機物，並獲得每小時的即時數據。
根據過往經驗，質譜儀離子源易受水氣干擾，導致一週內即需停機維護，本研究使用Agilent商業化注氫技術 (Jetclean)，將微量高純度氫氣注入至離子源，透過通入氫氣進而緩解經由高溫氧化下易附著於離子源表面之周界環境複雜基質，從而延長離子源壽命並提升在線連續分析技術。
研究結果顯示實驗最佳參數為使用舊款 (Inert) 離子源、中孔徑離子通道
(Drawout plate)、高氫氣流速與搭配Jetclean線上模式，可使儀器整體運作時間大幅延長至21天。藉由最佳化參數建立相關品保/品管測試，檢量線相對標準偏差 (RSD) 為0.43% ~ 11.09%，R2值介於0.992 ~ 1.000，方法偵測極限為0.04 ~ 0.77 ppb，回收率介於94.3%
~ 124.3%，精密度RSD為1.3% ~ 7.4%之間，符合標準方法NIEA A715.16B之儀器規範。
本研究藉由Agilent開發之Jetclean技術有效延長儀器連續運轉時間至雙週以上，並為線上連續監測技術開拓不同於以往做法之眼界。對於未來應用
Online TD-GC/MS連續監測污染物時不僅可獲得即時HAPs連續數據，更能以每小時逐時數據回溯污染物之排放源。;Hazardous Air Pollutants (HAPs), also called air toxics, have become a subject of attention in recent years due to their effect on public health. Of these air toxics, the volatile organic compounds (VOCs) are the targets of interest in this study, called toxic VOCs. The current most common analytical method for toxic VOCs is to use surface treated stainless canisters with gas chromatography mass spectrometry (GC/MS) to form a offline method, because the monitoring results are not obtained immediately. The data cannot effectively reflect the instantaneous characteristics of an emission source. As a result, this research continued
to improve the online method of Thermal Desorption Gas Chromatography / Mass Spectrometry (TD-GC/MS) with a water removal solution to achieve hourly measurements of 86 toxic VOCs.
From the past experience, the ion source of the mass spectrometer is easily contaminated by moisture in the sample, resulting in weekly cleaning of the ion source. This study used a commercial Jetclean technology by Agilent by directly introducing a small flow of high-purity hydrogen into the ion source. The complex sample matrix, which is oxidized at high temperature and prone to adhering to the surface of the ion source can be greatly alleviated by the addition of hydrogen, thereby extending the lifetime of the ion source and improving the continuity of the online technique.
The research results show that the optimal combination of parameters for extending the ion source’s lifetime is the use of the Inert ion source, the 6 mm drawout plate, the high hydrogen flow rate at 0.53 mL/min, and the online Jetclean mode. By doing so, the lifetime can be effectively
prolonged the monitoring time length to 21 days. Under the optimized condition, the quality assurance/control (QA/QC) results are as follows: the relative standard deviations (RSD) of the calibration curves ranging from 0.43% to 11.09%, linearity (R2) ranging from 0.992 ~ 1.000, MDL between 0.04 and 0.77 ppb, the recoveries between 94.3% and 124.3%, and the precision (RSD) results between 1.3% and 7.4%. All the QA/QC aspects complied with the specifications set by the NIEA A715.16B method.
This research used Jetclean technology developed by Agilent to successfully prolong the continuity of the online measurements to more than two weeks and thus broaden the prospect of of online monitoring of toxic VOCs. As a result, for future applications of the online TD-GC/MS technique, not only can one obtain the reliable instantaneous concentrations of toxic VOCs, but also allow back-tracking pollution sources from the spikes of the hourly data. |
