The invention relates to a system and a process for fractionating a solution into two or more fractions. The system of the invention comprises at least two compartments having a diameter of at least about one meter and including a uniform packing of a polymer-based ion exchange resin with a bead size in the range of about 50 to about 250 .mu.m. The mixing volume of the fluid fronts in the system of the invention is not more than 5% of the volume of the compartment.