Operationally defined extraction procedures for soil and sediment analysis - I. Standardization

Environmental studies on soil and sediment analysis are often based on the use of leaching or extraction procedures (e.g. single or sequential extraction procedures) which enable broader forms or phases to be measured (e.g. 'bioavailable' forms of elements) and which are, in most cases, sufficient for the purpose of environmental policy. However, the lack of uniformity in the procedures used often hampers comparison of the results, owing to their 'operationally defined' character. This implies that the 'forms' of metals are defined by the determination of extractable elements, using a given procedure and, therefore, the significance of the analytical results is highly dependent on the extraction procedures used. The comparability of results can hence only be achieved if similar procedures are applied, which justifies efforts towards standardization. This article describes case studies of standardization approaches for single and sequential extraction procedures applied to soil and sediment analysis. In particular, the strategy followed by the Standards, Measurements and Testing program (formerly BCR) is fully described (feasibility study, interlaboratory studies and establishment of standardized protocols based on the results of tests and participants' experience). (C) 1998 Elsevier Science B.V.