The invention relates to a method for removing a viral contaminant from a preparation, being a cell culture medium or at least a component of a cell culture medium. The method comprises subjecting said preparation to filtration for at least about 24 hours through a virus filter having an effective pore size of maximum about 75 nm. Further, the invention relates to the use of a virus filter in filtration of at least about 24 hours, wherein the virus filter has an effective pore size of maximum about 75 nm for the removal of viral contaminant from a preparation, being a cell culture medium or at least a component of a cell culture medium. In some embodiments the filtration according to the invention operates at a volumetric capacity of at least about 2000 L/m2. Further, the invention relates to the use of a preparation, being a cell culture medium or at least a component of a cell culture medium obtainable according to method of the invention for cell culture; pharmaceutical, diagnostic and/or cosmetic preparations as well as in food preparations.