Comparative Chromatographic Method for Rapid Screening of Target Ionic Liquids

Analytical chemists learn the polarity of chromatographic stationary phase by testing the Rohrschneider-McReynolds constants in chromatographic columns, while chemical engineers acquire the selectivity and solubility of solvents by determining solubility parameters. However, in evaluating the properties of ionic liquids, they are not as useful as in general solvents. Sometimes the probe molecules have no peaks, and sometimes the solubility parameters calculated are not as what we predict. In order to overcome the shortages of the existing methods, a comparative chromatographic method was established, in which a well-known ionic liquid was used as a reference stationary liquid into the reference column, and new design ionic liquids as a sample stationary liquid filling into the sample column. With 7 solvents(n-hexane, ethyl acetate, benzene, 2-ketone, pyridine, n-butanol and nitro propane) as probe molecules, the adjusted retention time and asymmetry factor as the index, the target ionic liquids can be selected.