Phase equilibrium and chloramphenicol partitioning in aqueous two-phase system composed of 1-hydroxylhexyl-3-methylimidazolium chloride-salt

The phase equilibrium and chloramphenicol (CAP) partitioning in the aqueous two-phase system (ATPS) composed of 1-hydroxylhexyl-3-methylimidazolium chloride (HO[C6mim][Cl]) and K2CO3/K2HPO4/K3PO4 were studied. The binodal curves and tie-lines were given and correlated by the empirical equations that give satisfactory fitting effect. The effects of salts and temperature on phase equilibrium were discussed. The results show that the ability of the investigated salts for phase separation follows the order: PO43 − > HPO42 − > CO32 −; temperature has little influence on the phase diagram for the investigated systems. Furthermore, the influence factors of salts concentration and extraction temperature on partition behaviors of CAP were studied. Results revealed that the partition coefficients of CAP increase with increasing salts concentration in the HO[C6mim][Cl]-K2HPO4/K2CO3 ATPSs, which suggests that the salting-out effect is important for the transfer of the CAP. In addition, the temperature greatly influences the CAP partition. Thermodynamic studies indicated that the transference of CAP from the K2CO3-rich phase to the HO[C6mim][Cl]-rich phase is an exothermic process and it is necessary to control the temperature to achieve the maximum extraction efficiency.