Certified reference materials for the quality control of rare earth element determinations in the environment

The European Commission (through its BCR activity) is active in organising interlaboratory studies, the final aim of which is the production of Certified Reference Materials (CRMs) representing the best of the state of the art in given analytical sectors. As a response to needs expressed by laboratories for environmental reference materials certified for rare earth elements (REEs), a programme was launched in 1996, starting with a feasibility study (interlaboratory comparison). Four CRMs were produced and certified for a range of REEs, such as Sc, Y and the lanthanides (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu). This article outlines this programme and describes the materials produced, namely estuarine sediment (BCR-667), mussel tissue (BCR-668), aquatic plant (BCR-670) and calcareous soil (BCR-690). Details of the production, homogeneity and stability of the reference materials are given. The results of the certification are evaluated from a technical and a statistical point of view.