Hydrophilic organic/salt-containing aqueous two-phase solvent system for counter-current chromatography: A novel technique for separation of polar compounds

Hydrophilic organic/salt-containing aqueous two-phase system composing of ethanol, water and ammonium sulfate for separation polar compounds was investigated on multilayer coil associated with J-type HSCCC devices. Compared to the classical polar solvent system based on 1-butanol–water or PEG1000–ammonium sulfate–water, the water content of upper phase in ethanol–ammonium sulfate–water systems was from 53.7% to 32.8% (wt%), closed to PEG1000–ammonium sulfate–water aqueous two-phase systems and higher than 1-butanol–water (22.0%, wt%). Therefore, the polarity of ethanol–ammonium sulfate–water is in the middle of 1-butanol–water and PEG–ammonium sulfate–water system, which is quite good for separating polar compounds like phenols, nucleosides and amino acids with low partition coefficient in 1-octanol–water system. The retention of stationary phase in four elution mode on type-J counter-current chromatography devices with multilayer coil column changed from 26% to 71%. Hydrodynamic trend possess both intermediate and hydrophilic solvent system property, which closely related to the composition of solvent system. The applicability of this system was demonstrated by successful separation of adenosine, uridine guanosine and cytidine.