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Determination of heparin in aqueous solutions
B Demoré1, E Benoit, P Maincent
1Laboratoire de Pharmacie Galénique et Biopharmacie, Faculté des Sciences Pharmaceutiques et Biologiques, Nancy, France.
Objective:
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 end-point 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.