Comparison of the standard SM&T sequential extraction method with small-scale ultrasound-assisted single extractions for metal partitioning in sediments

A single extraction method based on the reagents employed in the SM&T (standards, measurement and testing programme) sequential extraction scheme for partitioning of Cd, Cr, Cu, Ni, and Pb in sediments has been developed. Small-scale extractions adapted to electrothermal atomic absorption spectrometric determinations (i.e. 25 mg mass in 1 mL extractant) have been used for the first time in conjunction with selective reagents using conventional operating conditions (i.e. conductive heating, magnetic stirring) or ultrasound-assisted extraction. Small-scale slurry preparations were implemented for determination of the residual/total metal content. The methodology developed enabled drastic reduction of extraction times, yielding extractable contents in accordance with those obtained by application of the conventional SM&T method, which can be regarded as a standard method. An important saving in the amount of sample and reagents is also achieved with small-scale extractions. Homogeneity of sediments at the mg level proved acceptable - precision was similar for between-batch and within-batch measurements. Method development was performed with CRM BCR 601 lake sediment for which extractable amounts of several metals are known. An application to a "real-world" sediment is also presented.