A mechanism of the high frequency AC iontophoresis

The efficiency and the voltage dependence of the AC iontophoresis were stud ied in vitro. Two cylindrical glass cells separated by a cellophane film we re used, where the donor cell was filled with the solution of target electr olytes and the receptor cell with distilled water. The sinusoidal AC voltag e with a frequency of 1 kHz was applied between the two platinum plates loc ated at the opposite ends of two cells. The time variation of the ion conce ntration was evaluated by measuring the impedance of the solution in the re ceptor cell. The transportation velocity of the ions increased with the amp litude of the voltage applied between two platinum plate electrodes apart 2 0 mm up to similar to 15 V, and levelled off above similar to 15 V.A theore tical model is proposed on the AC iontophoresis, where each ion moves toget her with the surrounding water molecules when it is hydrated. The effective Stokes radius of an ion is assumed to be half of the whole size of the ion with hydrating water molecules. When the external alternating electric fie ld strongly vibrates the ion, the ion-dipole interactions between the ion a nd water molecules are broken, resulting in the reduced effective Stokes ra dius, which leads to the increase of the diffusion efficiency. (C) 2001 Els evier Science B.V. All rights reserved.