It is demonstrated that the separation of diastereoisomers; and enantiomers can be accomplished by the flow-through partial-filling affinity CE using a crossreactive mAb. This approach revealed differences in the binding strength of the (+/-)-cis- and (+/-)-trans-benzo[a]pyrene tetrols with the anti-polycyclic aromatic hydrocarbon mAb and demonstrated that (+)-enantiomers are more strongly immunocomplexed than their (-)-counterparts. It is proposed that crossreactive monoclonal antibodies (i.e. mAb raised against achiral molecule and possessing limited selectivity) could be effectively utilized for specific stereoisomeric differentiation and chiral separations.