Dextran, a polysaccharide made from glucose, is widely used in the medical field for treatment of shock, as an antithrombotic agent, to reduce blood viscosity, and as an anticoagulant. The two most common forms are dextran 40 and dextran 70 (the 40 and 70 refer to their molecular weights, nominally 40,000 and 70,000 g/mol).
The USP monographs for dextran 40 and 70 describe a specific gel permeation chromatography approach that differs in success criteria from other GPC methods, and requires a unique GPC system setup and data analysis method. To qualify a dextran formulation under these USP guidelines, the material must be tested by this GPC method.
A calibration curve is constructed with dextrose and five dextran standards of known molecular weights, using either a Gauss-Newton method or the Nilsson-Nilsson method to determine the constants in the expression below for each of the standards based on their reported molecular weights Mi.
Mi = b5 + exp(b4 + b1Ki + b2Ki2 + b3Ki3)
Each of the standards must meet a rigorous accuracy check to ensure the GPC system is adequately set up to test the specific dextran samples and to ensure they meet the requirements of the USP monographs. Once the equipment is properly validated by this method, the samples can be tested.