Study on the analysis of freon substitutes in the atmosphere

本研究以气相色谱-质谱联用技术（GC-MS）为基础，建立了大气中氯氟烃（CFCs）及其替代物的检测技术。采用QP-5000（Shimadzu）和VOCOL柱（Sigma Aldrich）60 m长× 0.25 mm内径分别作为GC-MS和分析柱。作为初步实验，进行了GC-MS的性能测试，考察了该检测器对CFCs及其替代物和大气中主要卤代烃如氯仿、四氯化碳、1，1，1-三氯乙烷的最低检出限和特征响应。建立了空气样品组分浓缩装置和工业标准气体稀释校准系统。VOCOL色谱柱的优点是可以沿着测定主要的卤代烃以及目前日益增加的替代品HCFC-141 b和142 b。但缺点是未知物质对最低沸点的HCFC-22和HFC-134 a的峰有干扰。仅给出了HFC-134 a的上限浓度。对于挥发性较高的化合物，应使用PLOT柱，以改善色谱峰的分离。对位于东京北方郊区的东洋大学川越校区采集的样本进行分析的结果显示，HFC-134 a、HCFC-141 b和-142 b的浓度差异很大，分别为12- 32 ppt、10- 30 ppt和12- 75 ppt。相反，卤烃类被禁止使用，CFCs、CCl_4和CH_3CCl_3被发现相对稳定。

In this study, basic experiments were made to develop a measurement technique for chlorofuorocarbons (CFCs) and their substitutes in the atmosphere by gas chromatography with mass spectrometric detection (GC-MS). QP-5000 (Shimadzu) and VOCOL column (Sigma Aldrich) 60m long by 0.25mm inner diameter were used as GC-MS and analytical column, repectively. As a preliminary experiment, performance tests of GC-MS were made to examine the lowest detection limit and the characteristic response of the detector to CFCs, their substitutes and major atmospheric halocarbons such as chloroform, carbon tetrachloride, 1,1,1-trichloroethane. An apparatus concentraing the components of air samples and a calibration system to dilute commercial standard gases were constructed. The advantage of VOCOL column is that the major halocarbons can be determined along with the currently increasing alternatives, HCFC-141b and 142b. However the disadvantage is the interference of unknown spccis to the peaks of HCFC-22 and HFC-134a, both of which are of lowest boiling point. Only upper limit concentration is given for HFC-134a. A column for compounds of higher volatility, PLOT column, should be used to improve the chromatographic separation of the peaks. Analytical results for sumples collected in the Kawagoe campus of Toyo University, which is located in the northern suburbs of Tokyo, showed a large difference in the concentrations of HFC-134a, HCFC-141b and -142b, being 12-32ppt, 10-30ppt and 12-75ppt, respectively. On the contrary, the halocarbons banned the use, CFCs, CCl_4 and CH_3CCl_3 were found to be relatively constant.