The Determination of Twenty-three Trace Volatile Compounds in the Ambient Air by Thermal Desorption with Two-stage-cryogenic Focusing and GC-MS

• Main Authors: Ting, Su May, 丁素梅
• Other Authors: J. C. Gaston Wu
• Format: Others
• Language: zh-TW
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/60255714043832992042

碩士 === 國立臺灣師範大學 === 化學系 === 84 === The volatile organic compounds (VOCs) are important toxic pollutants in the ambient air which can affect human health. If one is exposed in the environment with high level of VOCs will cause physiological changes including DNA damages that may lead to cancer. Exposure to VOCs will also bring stimulation of mucous membrane of the breathway and eyes. Besides, VOCs can anesthetize the centeral nerve system. In order to estimate the effects of VOCs on our environment and toxic damagesto human physiology, analytical techniques for VOCs have been recently emphasized on developing procedures detect much more compounds and at lower concentrations. The instruments used in this work. Including thermal desorption system, GC-FID and GC-MS. In the process of analysis, internal standards with or without istopes are used to enhance the accuracy of determination. Low-volume-flow pumps are used to drive the air sample through the column packed with Tenax TA as adsorbent to collect VOCs. At first, VOCs in the sampling column are analytes desorbed at temperature of 180℃. Then are condensed in the cryo-trap by liquid nitrogen. Helium acts as carrier gas to drive the desorbed VOCs to GC. Finally, the analytes separated by a capillary column goes on for quilitative and quantitative analysis in MS. In this study, the overall recoveries range from 78.3％ to 109.8％. The rae of detection limits is 0.69 ngqsymbol 126 \f "Symbol" \s 12 ~ 6.32 ng. The relative standard deviations of relention times the range of 0.26％ symbol 126 \f "Symbol" \s 12 ~ 1.26％. The feasibility of this method is tested by real sample analyses from different sources.