Determination of heparin activity by a new laser nephelometric method and comparison to the USP method

A new method for the determination of heparin activity in solutions has been developed, based on the increase in light scattering observed during the clotting of plasma. The recalcification clotting time (RCT) of sheep plasma is measured in the presence of heparin, using a laser nephelometer. The activity of heparin in the sample is determined from a standard curve of the logarithm of RCT versus heparin activity. The results indicate that this method is simpler, faster, and more reproducible than the current USP grading method.