2. Diastereomer formation by precolumn derivatization

This method involves pre-reacting the racemate with an optically pure reagent to form diastereoisomers; these have different physico-chemical properties and can therefore be separated using conventional stationary and mobile phases. This method is limited to molecules with reactive functions (amines, acids, alcohols, etc.). For preparative separations, the return to the initial enantiomer may be accompanied by partial racemization, which is another limitation of this method.