To develop a volumetric method for assaying heparin in aqueous media.Method:
Heparin is precipitated out with an aqueous solution of an organic amine by titration and the endpoint is based on the measurement of the medium dielectric permittivity. We studied the titration of a 500 IU/ml heparin solution with a 0·08 M cetylpyridinium chloride solution at pH 6·8. Then, we assayed sulphate groups selectively at pH 2. The results were compared against a classical method of SO2 determination. The sensitivity and reproducibility of the volumetric method were evaluated at pH 6·8 and compared with the characteristics of a chromogenic method, usually used for the assay of heparin in biological fluids.Results:
A linear relationship between anticoagulant activity and sulphate and carboxyl group concentration was observed. The method was less sensitive but more reproducible than the chromogenic method.Conclusion:
The proposed method can be used for aqueous solutions and is easy to carry out. It can be fully automated and applied to formulation studies.