Comment on "Long-range electrostatic interactions between like-charged colloids: Steric and confinement effects"

In a recent study [Phys. Rev. E 60, 6530 (1999)], Trizac and Raimbault showed that the effective pair interaction between like-charged colloids immersed in a cylindrically confined electrolyte remains repulsive even when the size of the microions and the finite longitudinal extension of the confining cylinder are taken into account. Contrary to their claim, we argue that the case of finite longitudinal confinement does not always generate repulsive interactions and to illustrate this point we also provide a simple example.