Affinity capillary electrophoresis in binding study of antithrombin to heparin from different sources

► The binding of antithrombin (AT) to heparin is estimated by affinity CE. ► Binding constant (Kd) is determined for a number of heparins from various sources. ► In-vitro activity and saccharide composition of heparin samples are determined. ► A correlation between in-vitro activity and binding constant is found. ► Origin and saccharide composition are not related to the heparin affinity for AT.