Influence of mixing time and agitation speed on partitioning and mass transfer coefficient of cephalexin in aqueous two-phase systems.

Aqueous two‑phase systems (ATPSs) are widely used for biomaterial separations, yet their kinetic behavior and mass transfer mechanisms are less characterized than equilibrium properties. This study examined cephalexin partitioning and mass transfer in acetonitrile + glucose + water and PEG6000 + tri‑sodium citrate + water ATPSs, assessing the effects of mixing time (2-180 min) and agitation speed (300-900 rpm) on partitioning efficiency, mass transfer rates, and time to equilibrium. The results reveal that the acetonitrile + glucose ATPS demonstrated stronger partitioning with a quasi‑partition coefficient reaching 14.1 but required approximately 50 min to equilibrate, while the PEG6000 + tri‑sodium citrate ATPS attained equilibrium faster (≈ 30 min) with a slightly lower quasi‑partition coefficient of 12.5. The finding shows an enhanced mixing speed and longer mixing durations improved both partitioning and mass transfer, with mass transfer coefficients determined as 0.093 min⁻¹ and 0.0898 min⁻¹ for the respective systems at the optimum conditions; a correlation relating mixing speed to the mass transfer coefficient is also proposed. Consequently, the results emphasize that mixing conditions substantially influence ATPS mass transfer kinetics and highlight the importance of kinetic considerations alongside equilibrium properties.