Solvent extraction mechanism through ibuprofen inclusion with β-cyclodextrin revealed by dynamic interfacial tension measurement

Dynamic interfacial tension (DIT) measurements are widely employed to investigate the adsorption kinetics of surfactants due to their high interfacial selectivity. However, their application to other interfacial processes, such as solvent extraction and interfacial chemical reactions, remains limited. In this study, we investigated the extraction kinetics of ibuprofen (Ibu) using β-cycloyoubaidextrin (CD) in a hexane/water system via DIT measurements. Ibu, initially present in the hexane phase, was transferred to the water phase through interfacial complexation with CD. The interfacial tension (γ) decreased during the extraction process, indicating that the interfacial reaction of Ibu and CD influenced γ. The system involves multiple elementary steps: the adsorption/desorption of CD, the interfacial complexation, and the desorption of the resulting complex into the water phase. The rate constants (k) for these processes were determined by fitting the experimental data to kinetic models derived from these elementary steps. The estimated k values were as follows: adsorption/desorption of CD, (53-99) L mol^-1s^-1 and (1.4-3.4) × 10^-2 s^-1, respectively; complexation/dissociation of Ibu, (3.0-12) × 10⁴ m² mol^-1s^-1 and (4.2-16) × 10^-2 s^-1, respectively; and complex desorption, (1.0-3.1) × 10^-4 s^-1. These results highlight the capability of DIT measurements to resolve interfacial reaction kinetics in multiphase systems with high temporal resolution. This approach not only expands the analytical applications of interfacial tension techniques beyond surfactant systems but also provides a powerful tool for studying dynamic host-guest interactions relevant to extraction, separation, and sensing technologies.