The theory developed by De Lacey and White (E. H. B De Lacey and L. R. White, J. Chem. Soc, Faraday Trans 2, 1981, 77, 2007) to calculate the electrophoretic mobility of a solid, spherical colloidal particle subjected to an oscillating electric field is modified to include the inertial terms in the Navier–Stokes and colloidal-particle force balance equations. These inertial terms are extremely important in determining the mobility for frequencies above ca. 10⁵ Hz, particularly at large particle size.

The magnitude and phase of the electrophoretic mobility are displayed as functions of zeta potential, frequency, particle size and electrolyte concentration. The numerical results are compared with the De Lacey and white model and the approximate theories developed by O'Brien (R. W. O'Brien, J. Fluid Mech., 1988, 190, 71) and Babchin et al. (A. J. Babchin, R. S. Chow and R. P. Sawatsky, Adv. Colloid Interface Sci., 1989, 30, 111).

A program for calculating the electrophoretic mobility and other variable-frequency transport properties is available from the authors.