An appraisal of microwave-assisted Tessier and BCR sequential extraction methods for the analysis of metals in sediments and soils

The purpose of this research was to assess the precision and accuracy of a BCR and Tessier microwave-assisted sequential extraction procedure, in comparison to the conventional versions for a range of metals using a soil, lake and estuarine certified reference material (CRM). Four sequential extraction methods were run on the three different CRMs and the concentrations of Cu, Pb and Zn were analysed. Iron, Mn and Ca were also measured in each extract to determine the effect of the sequential extraction procedures on the sediment phases. Precision and accuracy of all four methods were very good and in line with values observed in the literature. The microwave-assisted sequential extraction procedures achieved results which were only broadly comparable to the conventional versions. Generally, the microwave procedures extracted lower concentrations of metals in the reducible phase, designed to attack the Fe and Mn oxides, and consequently the concentrations in the following fractions were higher. The microwave-assisted procedures were faster than the conventional procedures and provided accurate and precise results. However, it is clear that the same fractions of sediment were not attacked by the microwave and conventional procedures, and therefore results from microwave analysis may not be comparable to conventional. However, these microwave procedures provide a fast, cost effective alternative to the conventional method for screening purposes. In order to provide comparable results, more method development is required.