Gradient polyacrylamide gel electrophoresis for determination of molecular weights of heparin preparations and low‐molecular‐weight heparin derivatives

The M_r values of pharmaceutical heparins and low‐molecular‐weight (LMW) heparin derivatives were examined as part of a collaborative study to develop methods for their characterization. Standard methods of M_r determination rely on gel permeation high‐performance liquid chromatography (HPLC). We report the use of gradient polyacrylamide gel electrophoresis (PAGE) to determine the M_r values of pharmaceutical heparins and LMW heparin derivatives. This approach offers certain advantages over the HPLC method. Gradient PAGE analysis was performed in parallel, on multiple samples, with the same standard curve. HPLC was performed serially. Gradient PAGE gave higher resolution than HPLC, and thus, a mixture of easily obtained standards was used in place of individual standards for the construction of a standard curve. Heparin and various LMW heparin samples were analyzed by both gradient PAGE and conventional gel permeation HPLC methods. The number‐average M_r, weight‐average M_r, and polydisper‐sity were examined by both techniques and found to be similar. This study demonstrates that gradient PAGE analysis is a sensitive method for the determination of the M_r values of heparin and LMW heparin.