Preparation of a soil reference material for the determination of radionuclides

Method performance in analytical chemistry is checked using certified reference material (CRM). Due to their high production cost, CRMs cannot be used routinely in daily laboratory work, therefore, laboratory reference materials (LRMs) is preferred. This paper describes the preparation of an LRM for the determination of radionuclides in soil. The LRM was prepared by mixing three soils -two from areas affected by the Chernobyl NPP accident, which present condensed radioactivity contamination, and one non-contaminated soil from inland Catalonia. The resulting solid dilution contained condensed radioactive contamination at environmental levels and natural radionuclides (137Cs, 90Sr, 40K, 212Pb, 214Pb, 208Tl, 214Bi and 228Ac). Bulk homogeneity was checked before soil was bottled and, once bottled, final homogeneity and stability studies were performed. Analysis of variance was carried out with the results. No statistically significant differences were observed for within- or between-bottle results. Neither the storage temperature nor the time of the determination after bottling affected the results. Therefore, the material prepared is considered homogeneous and stable and will be used in a future intercomparison exercise for radiochemical laboratories in Spain.