In Situ Microscope Measurements and Analysis of the Passing of Individual Paramagnetic Particles through the Interfaces of Aqueous Two-Phase Systems by Magnetic Force

Abstract

The interfacial tensions of aqueous two-phase systems (ATPS) are commonly much lower than those of common oil/water interfaces. Micrometerto mm-sized particles tend not to pass through liquid/liquid interfaces and tend to be trapped there. In the present study, the passing of m-sized ferromagnetic and paramagnetic particles through ATPS interfaces was examined using a magnetic force by microscope observation. Ferromagnetic particles were aggregated at the ATPS interface under a magnetic field. Mn2+-adsorbed cation-exchange resin particles are not ferromagnetic but paramagnetic, and they were not aggregated. The individual Mn2+-adsorbed particles were drawn down from the interface by a downward magnetic force and then released. The forces on the particles, the gravitational force, the buoyancy, the magnetic force, and the force caused by the interfacial tension, were calculated or estimated from the experimental results. The present method is a fundamental study to develop a separation method for m-sized particles using liquid/liquid interfaces.