Interlaboratory comparison of EDTA and DTPA procedures prior to certification of extractable trace elements in calcareous soil

The use of single extraction schemes for soil studies is widely recognized. These procedures are currently performed in many laboratories to assess the bioavailable metal fraction (and related phyto-toxic and nutritional deficiency effects) and the accessability to the environment (e.g., contamination of ground waters). Owing to the need for validation of the extraction schemes used and of the analytical techniques, the EC Measurements and Testing Programme (formerly BCR) has organized a project for improving the quality of determinations of extractable trace metal contents in two soils (sewage sludge-amended and terra rossa soils), the first step of which was an interlaboratory study followed by a certification campaign for EDTA- and acetic acid-extractable trace metal contents. This project was complemented by an interlaboratory study on EDTA and DTPA extraction schemes applied to a calcareous soil reference material. The latter study was actually a feasibility study which allowed the necessary precautions to be set up for the use of these schemes prior to certification of a calcareous soil. This paper presents the results of this intercomparison.