Thermodynamic Parameters For Organic Solutes In Ionic Liquids And Study On [EMIM][Ac] Gas Chromatography Column

Compared with traditional organic solvents,ionic liquids(IL)are almost nonvolatile and have good solubility for a large number of inorganic and organic substances.It can be considered to replace the volatile traditional organic solvents commonly used in industrial production.In addition,due to the separation selectivity,good thermal stability and chemical stability of ionic liquids,they can be used as stationary phases for gas chromatography and coated on the capillary wall to prepare capillary columns for gas chromatography analysis.In this work,two ionic liquids,1-ethyl-2,3-dimethylimidazole thiocyanate([EDMIM][SCN])and 1-ethyl-3-methylimidazole acetate([EMIM][Ac]),were prepared,The infinite dilution activity coefficients(γi∞)of 31 organic solutes(alkanes,cycloalkanes,olefins,aromatic hydrocarbons,acetonitrile,acetone,tetrahydrofuran,ethyl acetate,1,4-dioxane,methyl chloride,alcohols,etc.)in two ionic liquids were determined by gas chromatography(GC)in a certain temperature range,and according to(γi∞)values.Based on the γi∞ values,gas-liquid partition coefficient(KL),partial molar excess enthalpy(HiE,∞),the entropies(TrefSiE,∞),and Gibbs free energies(GiE,∞)at T=298.15K were obtained.From the linear free energy model(LFER),the KL prediction model of ILs was established by multiple regression of KL experimental values.The solubility parameters of the two ILs were estimated according to Hildebrand Scatchard regular solution theory and Flory equation.In addition,based on the prepared packed column with[EMIM][Ac]as the stationary phase,the separation effect of various organics on the chromatographic column was predicted,and the results were applied to the assessing separation of capillary chromatographic column.By calculating the distribution ratio and relative retention values of the samples on the chromatographic column,the separation possibility of different components on the chromatographic column can be predicted.[EMIM][Ac]was selected as the stationary phase to fill the capillary column,and its separation ability was studied.By selecting the type of raw column,adjusting the control of filling pressure and carrier gas flow rate,and exploring the conditions such as coating,aging and separation efficiency of chromatographic column,the conditions for coating a capillary chromatographic column with good separation performance were obtained.