Preparative Gel Permeation Chromatography (GPC- Prep) is used for the fractionation of polymer samples on a preparative scale. The elution order is from high molar masses to low molar masses. Therefore, the method can be used for determination of oligomers content and purification of polymer sample (removal of low molecular weight impurities, e.g., residual initiator, additives). These low molecular weight components are eluted after the main fraction of the polymer and can be readily removed by “end-shaving”. The polymer fraction (up to 100 mg/run) can be recovered by removing the solvent (under vacuum). The Mn and Mw/Mn of the samples can be determined by the analytical GPC.