大氣中揮發性有機化合物以Tenax吸附採樣GC/MS分析方法之探討

Determination of Volatile Organic Compounds in Ambient Air Using A Sampling and Analytical Method of Tenax Resin Adsorption. Thermal Desorption Procedure, and Gas Chromatograph/Mass Spectrometer

詹長權(Chang-Chuan Chan) ； 林守香(Shou-Hsiang Lin) ； 何國榮(Guor-Rong Her)

《化學》 51卷3期 (1993/09) Pp. 273-286

https://doi.org/10.6623/chem.1993029

摘要

空氣中揮發性有機化合物(Volatile organic compounds, VQCs) 是空氣污染學界中極為重視的污染物之一。因為它們是光化學作用產生對流層臭氧(Tropospheric ozone) 的先驅化合物， 更是造成健康影響的重要空氣毒性污染物。長期暴露在低濃度VOCs下易引起一般俗稱的大樓症候群(Sick Building Syndrome)，此外對人體的神經系統、呼吸系統、造血系統和肝臟等亦會產生慢性的傷害，其中更有一些成份，如苯可導致血癌的發生。為評估VOCs在光化學作用及空氣毒性作用方面的影響，大氧化學界近年的研究已著重在發展一套可偵測較多種類的化合物和較低偵測濃度的採樣分析技術。本研究即針對大氣環境中低濃度的VOCs進行探討，嘗試利用熱脫附裝置將探集到的樣品脫附濃縮直線注入氣相色層質譜儀(GC/MS)中分析。空氣樣本的採集是利用低流幫浦(流速為30～50mL/min) 帶動空氣通過填充Tenax GC吸附劑(400mg) 的採樣管，將C5-C10的VOCs 吸附捕集。分析程序首先是以230℃的高溫將採樣管中的VOCs脫附出來用滋態氮將分析樣品冷凝濃縮於泠凝管，再以氦氧為載送氣體將脫附出來的VOCs載送到氣相分析儀中經長度為50 m的HP-1層析管柱分離後以質譜儀對大氣中的VOCs進行定性、定量的分析。分析測定結果發現熱脫附裝置的脫附效率可達98%，各主要分析的目標污染物的回收率測試範圍在80.9%～106.4%，偵測極限範圍在1.3 ng (0.1 ppb)～7.8 ng (0.4 ppb) ，故此採樣分析方法可運用於周界空氣中微量揮發性有機化合物的偵測。

並列摘要

The volatile organic compounds (VOCs) are important precursors of photochemical reactions in forming tropospheric ozone. Some of them are air toxies of causing adverse health effects, such as ＂sick building syndrome＂ from chronic exposure to all VOCs and leukemia from benzene exposure. In order to estimate ozone-forming potency and health effects from each individual VOC, new sampling and analytical methods of measuring VOCs at low concentrations are necessary. This study is designed to develop a sampling method for measuring ambient VOCS in fixed locations and in personal breathing zones and an analytical protocol to measure VOCs at ppb levels. We successfully demonstrated that Tenax GC sampling tubes (400mg sorbate) with low sampling rates (30-50 mL/min for 0.5-4 hours) were able to collect enough amounts of C5-C10 VOCS to be analyzed by a GC/MS system. In analysis, the YOCs were first thermally desorbed at 230℃ (Tekmar Inc., Model 5010 GT from Tenax GC and then cryogenically focused by liquid nitrogen at -120℃and finally carried into a 50m long HP-1 capillary column for separation and a quadrupole mass spectrometer (HP5971A) for identification and quantification. For most target VOCs, the desorption efficiency of thermal desorber was about 98%, the recovery efficiencies ranged from 80.9%-106.4%, and the detection limits ranged from 1.3ng-7.8ng (0.1 ppb-0.4 ppb) in ambient air.