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.