Abstract: A method of isolating a biomolecule from a medium containing biomolecules by ion exchange wherein the ion exchange material consists of a material having ion exchanging groups which can be transformed from a charged form to an uncharged form; the eluant comprises a charge neutralizing acid or base transforming the ion exchanging groups from the charged form to the uncharged form; and the charge neutralizing acid or base has a concentration in the eluant which is twice, preferably equal to or less than the concentration of the ion exchanging groups of the ion exchange material; the ion exchange material being in a packed, hydrated state. Preferably the method is for the isolation of phosphopeptides from a medium containing casein hydrolysates and the use of such isolated biomolecules is for the production of a food, a feed, a health care product, a cosmetic, or a pharmaceutical.