This Technical Specification specifies a test method to determine the mass fraction of a polymeric additive that falls below a MW of 1000. The method is applicable to polymeric additives per se - i.e. supplied in their usable form, before formulation into a plastic. The method is also applicable to polymeric additives extracted from finished plastic materials and articles, provided that precautions are taken to ensure the absence of any interference from any other co-extractives derived from the plastic.