Aqueous two-phase systems for cephalexin monohydrate partitioning using poly ethylene glycol and sodium tartrate dihydrate: Experimental and thermodynamic modeling

The partitioning of cephalexin monohydrate in aqueous two-phase system (ATPS) of polyethylene glycol (PEG) with different molecular weights (1000, 2000, 6000, and 8000) and sodium tartrate dihydrate salt was investigated. Equilibrium compositions of two liquid phases were obtained in each system. The experimental data were correlated using the extended NRTL and a modified UNIQUAC (UNIQUAC+DH) models by adding a Debye-Huckel term (DH) to original models for taking into account the long range forces term of activity coefficient of components. The results show that the molecular weight of the polymer has a considerable effect on the partition coefficient of cephalexin monohydrate. The comparison of results for presented models with the experimental data demonstrates that the investigated thermodynamic models can correlate the equilibrium composition very well. The extended NRTL model with AARD of 0.099 is superior to UNIQUAC+DH.