A sample independent statistic mathematical model was developed which describes the quality of separation of polymer blends by Crystallization Analysis Fractionation (CRYSTAF). By coupling the abstract model with experimental data, factors influencing the non-equilibrium CRYSTAF separation process of heterophasic polypropylene copolymers were determined. It could be shown that the stirring speed during CRYSTAF process strongly influences the quality of separation and thus the quality of the CRYSTAF profile obtained for a certain polymer. A new optimal fractionation method for CRYSTAF was designed which leads to CRYSTAF profiles of high quality. The results of the model were experimentally verified by application of the new method to three different polyolefin blends.