When polyelectrolytes (lignosulfonates) with a broad molecular weight distribution are eluted from Sephadex gels with water, the fractionation is affected by steric exclusion, polyelectrolyte expansion, ion exclusion, and ion inclusion effects. The ion inclusion effect is due to interaction of charged sites in the macro‐ions which are more or less excluded from the gel with charged sites in more permeable macro‐ions. The ion inclusion effect depends on the cation of the lignosulfonates in such a way that the elution of lignosulfonates with a univalent cation is affected to a greater extent than the elution of lignosulfonates with a divalent cation. This is due to the existence of a higher density of free charges in the lignosulfonates with a univalent cation owing to a lesser tendency to form ion pairs. By choosing suitable eluents, it is possible to alter the retention volumes of lignosulfonates of different sizes and thus optimize the resolution.