Gel permeation chromatography of dextrans in parenteral solutions: Calibration procedure development and method validation

We describe development and validation of a gel permeation chromatographic (GPC) method for dextrans in parenteral solutions. The GPC method was adopted from USP monographs on Dextran 40 and Dextran 70 raw materials. The method was optimized with a mobile phase flow rate of 1 mL/min and column temperature of 40 °C, to sharpen dextran and dextrose peaks. An easy-to-use, curve-fitting program capable of non-linear regression was developed in-house, using Microsoft Excel® and its Solver add-in to successfully meet the GPC calibration requirements for dextrans and dextrose, i.e., the experimental molecular weights within 100 ± 5% of the known molecular weights for dextrans and molecular weight of dextrose within 180 ± 2 Da. The GPC method was validated in terms of its stability indicating nature, robustness (column temperature of 40 ± 3 °C), accuracy (lack of effects of pH and concentration of dextrans or matrix components), and precision (repeatability and intermediate). Molecular weight distribution of dextrans were unchanged when the dextran containing test solutions were subjected to forced degradation using heat, light (daylight and UV light), extreme alkaline conditions or oxidative conditions. The method was capable of detecting changes in molecular weight distribution caused by degradation under extreme acidic conditions and heat, thereby confirming the stability indicating nature of the method. The concentration of Dextran 40 and Dextran 70 (75–125% of the nominal assay concentration), matrix components (108–111% of their nominal concentrations), and solution pH (pH 3–7 for Dextran 40 solutions and pH 4–7 for Dextran 70 solutions) did not affect the measured molecular weight distribution of Dextran 40 or Dextran 70. The method was precise with %R.S.D. of less than 1% for M¯W values of Dextran 40 or Dextran 70.