Magnetic susceptibility measurement of a microdroplet interface using a magnetic circuit

A conventional method to measure the magnetic susceptibility of a microdroplet in a glass capillary has been constructed by using a magnetic circuit (2.82 T) with a high magnetic field gradient (B(dB/dz) = 3900 T(2)/m). The magnetophoretic velocity of a toluene droplet with ferrocene dispersed in 1 M HCl aqueous solution including K(3)[Fe((III))(CN)(6)], Fe((III))Cl(3) and cetyltrimethylammonium bromide (CTAB) was measured and the volume magnetic susceptibility of droplets was determined. From the dependence of the magnetic susceptibility on the radius of the droplets, the interfacial magnetic susceptibility of the droplets adsorbed by Prussian blue aggregates was determined. The interfacial concentration of Prussian blue of individual droplet calculated from the observed magnetic susceptibility indicated that the interfacial concentration of Prussian blue are different even in similar sized droplets, suggesting inhomogeneous formation of interfacial aggregates.