Analysis of the magnetic force generated at a hemispherical microelectrode

An analytical expression is presented for the magnetic force generated during steady-state voltammetry at a hemispherical microelectrode immersed in a uniform magnetic field. Diffusion of electrogenerated ions through the magnetic field results in a magnetic force that induces convective solution now near the electrode surface. The magnetic force per unit volume, F-mag(v) (i.e., force density), is shown to decrease as r(-2), where r is the distance away from the center of the hemispherical electrode. A consequence of the inverse square dependence of F-mag(v), on r is that the magnetic force is confined to a microscopic solution volume near the electrode surface (e.g., similar to 2 x 10(-9) L for a 12.5-mu m-radius hemispherical electrode), The net magnetic force acting on the diffusion layer volume, F-mag(net), is computed as a function of magnetic field strength and orientation and used in an approximate analysis of experimental data obtained at an inlaid 12.5-mu m-radius Pt microdisk electrode. Enhancements in voltammetric currents are shown to result from magnetic forces as small as 2 x 10(-11) N.