Charge variants of a recombinantly expressed antibody population may be separated both from the main antibody molecule and from each other. Separation and isolation of charge variants may proceed via a combined modulation of salt concentration and pH during charge variant elution from a cation exchange support. Isolated charge variants may be assessed for their contribution to the potency of the overall antibody preparation. The make-up of an antibody preparation, at least in terms of the proportion of charge variants and of the main antibody can thus be controlled, for example, for biosimilar matching or for improving potency of the preparation.