Reproducibility testing of a sequential extraction scheme for the determination of trace metal speciation in a marine reference sediment by inductively coupled plasma-mass spectrometry

The sequential extraction scheme procedure recommended by the Bureau Commun de Reference (BCR) of the Commission of the European Communities is applied to a reference marine sediment (Standard Reference Material SRM 1646a) to test the reproducibility of a such chemical method. The 12 elements determined in the extracts are scandium, chromium, cobalt, nickel, copper, zinc, cadmium, tin, cesium, lead, thorium and uranium. Analysis of the extracts is carried out by inductively coupled plasma-mass spectrometry (ICP-MS). The adopted calibration strategy is external calibration with internal standardisation. The measurement of concentrations by more than one isotope per element allows to detect and overcome spectral interferences. The internal normalisation improves the long term precision, although the used internal standards appear not to be the best for the 45-238 mass range in such materials. The sequential extraction procedure is found to be reproducible enough for environmental studies of speciation. The sum amounts of trace metals released during the four different steps are similar to those released by total acid digestion of the sediment.