摘要：

Single or sequential extraction procedures have been developed in the 1980s to determine forms or phases of elements (e.g. 'bioavailable' forms of elements) in soils or sediments. The comparability of data is closely linked to the extraction procedures used, owing to the 'operationally-defined' character of these schemes, which was considered as a limiting factor. Within the last decade, efforts have been made by the European Commission (BCR programme and its successor SM&T programme) to harmonise single and sequential extraction schemes, with the final objective of certifying soil and sediment reference materials. The first part of the present review dealt with the aspects of standardisation/harmonisation of extraction schemes as applied to soil and sediment analysis. The second part concerned validation aspects of such procedures and described the preparation and certification of soil and sediment reference materials certified for their extractable trace-element contents, following harmonised single and sequential extraction procedures. The third part concerns an overview of the latest development on certified reference material (CRM) production regarding single and sequential extraction procedures applied to extractable trace-element contents.

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