Using binary mixtures of dicationic ionic liquids for determination of activity coefficients at infinite dilution by gas–liquid chromatography

This work is the continuation of our investigation into using dicationic ionic liquids (ILs) as stationary phase in gas chromatography (Tabar Heydar K, Nazifi M, Sharifi A, Mirzaei M, Gharavi H, Ahmadi SH, J. Chromatographia 76 (2013) 165). In this work, the activity coefficients at infinite dilution of 23 various solutes (alkanes, aromatics, alcohols, aldehydes, ketones, amines, chloroalkanes, ethers) have been measured in the two binary mixtures of ILs: 1,12-di(N-methylpyrrolidinium)dodecane–bis(trifluoromethylsulfonyl)imide/1,12-di(3-methylimidazolium)dodecane–bis(trifluoromethylsulfonyl)imide (1:1), [C12(mpy)2]–[(NTf2)2]/[C12(mim)2]–[(NTf2)2] and 1,12-di(N-methylpyrrolidinium)dodecane–bis(trifluoromethylsulfonyl)imide/1,12 di(3-methylimidazolium)dodecane–tetrafluoroborate (1:1), [C12(mpy)2]–[(NTf2)2]/[C12(mim)2]–[(BF4)2], by gas–liquid chromatography (GLC) in the temperature range from 313 to 343 K. The same operations were performed on the neat IL: 1, 12-di(N-methylpyrrolidinium)dodecane–bis(trifluoromethylsulfonyl)imide, [C12(mpy)2]–[(NTf2)2] at T = 313 and 323 K, in order to make a comparison between different ILs.These mixtures of dicationic ILs with different anions and the neat IL have been investigated in this study for the first time. Moreover, the solvation interactions between solvents and solute molecules at 313, 343 and 373 K have been determined via Abraham solvation parameter model (linear solvation free energy relationship [LSFER] model). The selectivities for the octane/linear alcohols, octane/polar compounds, cyclohexane/aromatics were obtained from experimental activity coefficient data at 313 K, and compared with other ILs from the literature. The result of this comparison confirms that these ILs are potentially excellent solvents for the separation of alkanes/alcohols, alkanes/polar compounds and aliphatic/aromatic mixtures.