FURTHER STUDY ON NAA IN CHARACTERIZATIONS OF REFERENCE MATERIALS

Characterizations of three major parameters of Certified Reference Mat erials (CRMs) concentration values of multielements, homogeneities of multielements, and stabilities of the materials, were further studied by NAA. In the determinations of multielements in RMs, both relative a nd K-0 (and its extension) standardizations were used in an effort to detect hidden systematic errors and expand the number of determinable elements. In the evaluations of multielemental homogeneities, double s ampling constants as well as Ingamells' Ks and F-test woe used to esta blish semi-quantitative expressions of sampling uncertainty vs. size a nd number of subsamples for given elements in given materials. For the investigation of the stabilities of certified values, K-0 NAA is to b e used in follow-up analyses to test variations of certified values an d provide updated and/or newly determined data. The final goal is to m ate NAA a definitive method for multi-trace element certification, a r eliable method for homogeneity characterization, and a reproducible me thod for stability test Examples are given to show preliminary results on the above aspects.