Heparin: a chiral mobile-phase additive for capillary zone electrophoresis

Heparin, a naturally occuring, polydisperse, polyanionic glycosaminoglycan, was investigated as a chiral selector for capillary zone electrophoresis. Baseline separations were obtained for a variety of underivatized drugs including antimalarials and antihistamines. Analysis was carried out at a pH of 4.5 or 5 using 2% heparin (w/w) in a 10 mM phosphate buffer under an applied voltage of 15 kV. All of the solutes successfully resolved contained at least two nitrogens with one of the nitrogens incorporated in a heterocyclic aromatic ring. Further, successful enantioresolution seemed to require that the nitrogens be somewhat distant from each other in the molecule. The results suggest that, in addition to electrostatic interactions, solute size may also play a role in the heparin chiral recognition mechanism.