Determination of plasma heparin by polybrene neutralization.

A method for determining heparin activity (in unit/ml) in human plasma is described. The method is based on neutralization of heparin by Polybrene , a polymerized quaternary ammonium salt. It uses serial incubations of plasma with increasing amounts of Polybrene in conjunction with thrombin-induced coagulation times to define the amount of Polybrene required to neutralize heparin in the sample. Reference curves involve linear relationships between amounts of Polybrene required to neutralize known amounts of heparin. Coefficients of variation for the assay vary from 4 to 10% over the range of 0.05 to 1.0 unit/ml.