Certified reference materials for the quality control of EDTA- and acetic acid-extractable contents of trace elements in sewage sludge amended soils (CRMs 483 and 484)

The ecotoxicity and mobility of trace elements in soils are often evaluated through analytical results resulting from operationally-defined determinations (single and sequential extractions), e.g. based on EDTA, acetic acid etc, extractions. The significance and comparability of these results is highly dependent on the procedures used (standardized protocols or standards adopted by international bodies) and their quality control relies on the availability of reference materials certified following these strictly applied procedures. Recognizing the need to harmonize some of the extraction schemes currently used for soil analysis, the Measurements and Testing Programme (formerly BCR) has organized a series of interlaboratory studies, the first aim of which was to evaluate EDTA- and acetic acid-extraction procedures and the second objective was to certify reference materials for their extractable trace element contents. Two sewage amended soils have been prepared for this purpose, originating respectively from Scotland and Catalonia. This paper describes the preparation, homogeneity and stability studies, and gives an overview of the certification campaign.