ABSTRACT
Countercurrent chromatography is a separation technique for the isolation of a mixture using a liquid stationary phase held in place by centrifugal force. Many texts are available that describe countercurrent chromatography and related instrumentation. Ionic liquids phase behavior can be varied and used to produce two, three or four-phase solvent systems in combination with conventional molecular solvents. The most common classification of ionic liquids is whether they are either hydrophobic or hydrophilic. The phenomena of the very low solubility of hydrophobic ionic liquids in water and non-polar solvents like hexane are very important in ionic liquid–liquid chromatography. The original attraction-repulsion principle has been updated to accommodate the different behavior of ionic liquid containing biphasic eluents. For the partitioning of the analyte into the starting biphasic solvent system, which has been chosen to have high solubility of the analyte, the ideal partition coefficient should be between 0.75 and 3.0.
