Assay of Heparin
Heparin is an injectable anticoagulant, nowadays usually made synthetically. It is used both as an anticoagulant in people, and in various medical devices such as test tubes and extracorporal circulation devices such as renal dialysis machines. Native heparin is a glycosaminoglycan with a molecular weight ranging from 6 to 40 kDa. The average molecular weight of most commercial heparin preparations is in the range of 12 to 15 kDa. Heparin consists of alternating units of sulfated D-glucosamine and D-glucuronic acid.
The anticoagulant activity of heparin is determined in vitro by comparing its ability to delay the clotting of recalcified citrated sheep plasma. Different methods for determining the onset of clotting are used. A minimum of three dilutions are prepared (for the standard and test preparation) and the associated clotting time is determined.
The assay should be analyzed by transforming the clotting times to logarithms. The results may be calculated easily with the help of PLA 2.0 and the combined potency estimates are obtained.
