Investigation of non-equilibrium separation time on the partitioning of cephalexin in an aqueous two-phase system composed of glucose and acetonitrile

Abstract In order to commercialize aqueous two-phase systems (ATPSs), not only the equilibrium data is essential, but also the knowledge of separation mechanisms, kinetics, settling time, and operational conditions are needed. Mixing duration and settling time are the most critical factors affecting separation and biomolecule partitioning in terms of economic aspects. This research aimed to find the desired conditions for separating cephalexin in an ATPS consisting of acetonitrile, glucose, and water. Firstly, the evolution of the interphase region was observed. Hereafter, to examine the effect of time on the experimental tie-lines and partition coefficient in non-equilibrium states, the settling time was varied from 2 min to 24 h. In addition, centrifugation was applied to help the separation at different time intervals and rotational speeds. The results of tie-lines slope and partitioning coefficients showed that the system approaches equilibrium after 5 h. However, using the centrifuge separation at 4000 rpm improved the separation time to 45 min, reaching 80 % of the actual partition coefficient. It can be concluded that with an acceptable tolerance in the partition coefficient, a remarkably diminished settling time is available for economic productivity in industrial units.