We analyze the electrophoretic motion of a freely
suspended closely fitting sphere, eccentrically positioned within an infinitely
long cylindrical pore, when subjected to a uniform electric field acting
parallel to the pore. The thin Debye-layer approximation
is employed. Using singular perturbation expansions, the fluid domain is
separated into an "inner" gap region around the sphere's equator,
wherein electric field and velocity gradients are large, and an
"outer" region, consisting of the remaining fluid domain, wherein
field variations are moderate. Laplace's equation is solved within the gap region using stretched
coordinates, whereby matching with the outer solution is facilitated by use of
an integral conservation equation for the electric field flux. Using a
reciprocal theorem, the electrokinetic contributions
to the force (torque) on the sphere are represented as quadratures
of the electric field over the sphere surface, with the respective stress
fields pertaining to purely translational (rotational) motions appearing as
Green's functions. The translational velocity of a concentrically positioned
sphere is found to be half that for a sphere in an unbounded fluid. Both the
translational and rotational sphere mobilities
increase in magnitude with increasing eccentricity.