Problems in the application of the three-step BCR sequential extraction to low amounts of sediments: an alternative validated route.

Poor recoveries are obtained if the BCR three-step sequential extraction is applied to 100 mg specimens rather than to 1 g. It is observed that analytes are lost during each phase separation which is carried out via centrifugation and can be hardly quantitatively performed on 100 mg sediment specimens. An alternative procedure, which is carried out on a single empty SPE column and involves separation by filtration, is developed to solve this problem. The proposed method is validated on 100 mg samples of certified sediment (BCR-701), but could be potentially used for even lower sediment specimens. Problems related to pH stability during step 2 and its influence on recoveries is also reported.