Study on the analysis of freon substitutes in the atmosphere

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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.