Preparation of the bovine liver 12-02-01 reference material and the certification of element contents from an interlaboratory comparison

Interlaboratory analysis of IRM NSC-21 Compost Vitahum

The preparation of internal reference material NSC-21 Compost Vitahum, including its stabilization, homogeneity testing, and evaluation of an interlaboratory comparison in which 19 laboratories took part using several analytical methods is described. From the results of the intercomparison, consensus values were derived for the contents of Cd, Cu, Ni, Pb, and Zn, whereas for As, Co, Cr, Fe, Hg and Mn, information values were derived. Bimodal distribution of the As and Cr results was obtained, presumably because of incomplete dissolution of the elements from the matrix if insufficiently aggressive decomposition procedures were employed. Some problems encountered were elucidated by application of neutron activation analysis (NAA) in its nondestructive and destructive (radiochemical) modes.

Accurate determination of cobalt traces in several biological reference materials

A newly devised, very accurate ("definitive") method for the determination of trace amounts of cobalt in biological materials was validated by the analysis of several certified reference materials. The method is based on a combination of neutron activation and selective and quantitative postirradiation isolation of radiocobalt from practically all other radionuclides by ion-exchange and extraction chromatography followed by gamma-ray spectrometric measurement. The significance of criteria that should be fulfilled in order to accept a given result as obtained by the "definitive method" is emphasized. In view of the demonstrated very good accuracy of the method, it is suggested that our values for cobalt content in those reference materials in which it was originally not certified (SRM 1570 spinach, SRM 1571 orchard leaves, SRM 1577 bovine liver, and Czechoslovak bovine liver 12-02-01) might be used as provisional certified values.