Study on the analysis of freon substitutes in the atmosphere

本研究采用气相色谱-质谱仪(GC-MS)对大气中的氯氟烃(CFCs)及其替代品进行了基础实验研究。色谱柱为QP-5000(岛津)和VOCOL柱(Sigma Aldrich)，柱长60m，内径0.25 mm。作为初步实验，进行了GC-MS的性能测试，考察了检测器的最低检出限和对氯仿、四氯化碳、1，1，1-三氯乙烷等主要大气卤素及其替代品的响应特性。建立了空气样品组分浓缩装置和商业标准气体稀释校准系统。VOCOL色谱柱的优点是可以与目前正在增加的替代品--HCFC-141b和142b一起确定主要的卤代烃。然而，缺点是未知的特殊化学品对沸点最低的HCFC-22和HFC-134a的峰有干扰。只给出了HFC-134a的上限浓度。对于挥发性较高的化合物，应使用PLOT柱，以改善峰的色谱分离。对位于东京北郊的东洋大学河口校区采集的样品的分析结果表明，HFC-134a、HCFC-141b和-142b的浓度相差很大，分别为12-32ppt、10-30ppt和12-75ppt。相反，禁止使用卤代烃，CFCs、CCl_4和CH_3CCl_3相对恒定。

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.