The standard specifies a general method for determining the average molecular mass and molecular mass distribution of polymers from using SEC-LS, i.e. size-exclusion chromatography (SEC) coupled with light scattering detection (LS). The average molecular mass and the molecular mass distribution are calculated from data of molecular mass and mass concentration determined continuously at eacht elution time. The molecular mass at each elution time is determined absolutely by combining a light scattering detector with a concentration-sensitive detector. Therefore this method is classified as an absolute method (see Clause A.1 in Annes A).