The invention is directed to a method for separating two or more seed fractions having different germination quality, to a method for preparing a seed fraction enriched in seed quality, and to the use of a magnetic field. The method for separating two or more seed fractions having different germination quality comprises: mixing a feed of seeds comprising seeds with at least two densities with a magnetic fluid thereby obtaining a mixture, and applying a magnetic field to the mixture such that the mixture is exposed to a magnetic gradient so as to separate two or more seed fractions with different densities.