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 imm ersed in a uniform magnetic held. Diffusion of electrogenerated ions t hrough the magnetic field results in a magnetic force that induces con vective solution now near the electrode surface. The magnetic force pe r 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 hemispheri cal electrode. A consequence of the inverse square dependence of F-mag (v), on r is that the magnetic force is confined to a microscopic solu tion 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 forc e acting on the diffusion layer volume, F-mag(net), is computed as a f unction of magnetic field strength and orientation and used in an appr oximate analysis of experimental data obtained at an inlaid 12.5-mu m- radius Pt microdisk electrode. Enhancements in voltammetric currents a re shown to result from magnetic forces as small as 2 x 10(-11) N.