Study On Chlorofluorocarbons Impurities In Medical HFC-134a By GC-MS

Chlorofluorocarbons(CFCs)were widely used as refrigerants,foaming agents, solvents,cleaning agents and fire extinguishers,but they are ozone depletion substances(ODS)and contribute to global warming.To protect the ozone layer,the Montreal Protocol stipulates the CFCs must be phased out and substitutes for CFCs must be found.HFC-134a(1,1,1,2-tetrafluoroethane)has been generally accepted as a promising and environmentally friendly CFC-12(difluorodichloromethane) alternative.The great developments have been taken placed for HFC-134a using as the medicaments,so it is necessary to qualitative and quantitative analysis of micro-impurities in medical HFC-134a in this thesis.This thesis contains the following three parts:1.Qualitative and quantitative analysis of micro-impurities in medical HFC-134a.The impurities in medical HFC-134a were qualitatively analyzed by GC-MS using the HP-PLOT Al₂O₃ S capillary column.And GC-FID was used to quantitatively analyze the micro-impurities.The detection limits of impurities are lower than 0.7μL·L^-1,the relative standard deviations are lower than 6.3%,the recoveries are from 90.0%to 120.0%,the linear ranges are in a range of 1.0～10⁵μL·L^-1, and the linearity correlation coefficients are more than 0.9990.In the experiment,eight impurities are determined in medical HFC-134a,and relative mass calibration factors of the CFCs impurities were also been determined,which was helpful to determine the content of the CFCs in others samples for the chemistry analytical laboratories without reference standards.Operation of the method is simple,fast and applicable to the routine quality analysis of medical HFC-134a.2.Study on availability of carrier gas in GC-MS analysis.In this paper,it was studied that a mixture(including almost all kinds of familiar organic compounds)was separated by GC-MS with different cartier gas(hydrogen,helium gas).The changes of MS peak value of each component were also been studied.After analyzing the results, a conclusion was gained:saturated hydrocarbon,benzene et al.can be analyzed when carrier gas is hydrogen,and the separating efficiency is high.While the nitro-compounds were easy to be deoxidized by hydrogen,so it is not proper for nitro-compounds to be analyzed when hydrogen was used as carrier gas.3.The study of adsorption characterization of CFCs onto clay minerals by inverse gas chromatography.In the experiment,adsorption properties(enthalpy of adsorption,entropy of adsorption as well as free energy of adsorption)and adsorption activated energies of several CFCs onto natural and surfactants modified clay minerals (bentonites,rectorite clays and activated clays)were calculated by means of determining their retention times and the corresponding peak areas in the temperature range of 40-100℃by inverse gas chromatography(IGC).(1)The difference of thermodynamic parameters of probing molecules on different clay minerals mainly depended on the interlayer spacing of clay mineral crystalloids and the surface polarity. It could be found that the CFCs were easy to be adsorbed onto the clay mineral which has the wider interlayer spacing and the stronger polarity of the surface.(2)The higher the E,values and the less adsorption enthalpies were,the more difficult probing molecules were be adsorbed onto the clay minerals.(3)The study of adsorption characterizations of CFCs onto clay minerals by IGC was helpful to farther understand the interaction of the CFCs and the clay granules in the atmosphere,which was expected to apply to reduce their atmospheric lifetimes and the global wanning potentials,and then the atmosphere environment would be well protected.