Partitioning of Cephalexin in Ionic Liquid Aqueous Two-Phase System Composed of 1-Butyl-3-Methylimidazolium Tetrafluoroborate and ZnSO4

Ionic liquid aqueous two-phase system (ILATPS) was applied in the extraction and separation of hydrosoluble antibiotics. The partitioning behavior of cephalexin (CEX) in 1-butyl-3-methylimidazolium tetrafluorob orate ([Bmim]BF4)-ZnSO4 aqueous two-phase system was studied by the partitioning parameter of the extraction efficiency. The effect of the volume of [Bmim] BF4, the concentration of ZnSO4, temperature, pH, and the volume of ZnSO4 solution was discussed concretely. When the volume of [Bmim] BF4 was 2 mL and the concentration of ZnSO4 was 35%, the extraction efficiency of CEX could reach 92.64% with pH unadjusted. The effect of the volume of [Bmim] BF4 on the extraction efficiency was higher than that of the concentration of ZnSO4. The temperature influenced not only the formation of aqueous two-phase system but also the extraction efficiency of CEX. The target was found to be preferentially extracted to the [Bmim] BF4-rich phase at the pH below 4.3. The partition of CEX to the top phase was enhanced by increasing the volume of [Bmim] BF4, the concentration of ZnSO4, and temperature; however, the partition of CEX to the top phase increased by decreasing the pH.