IntroductionRisk assessment related to trace metals (TM) in environmental solids is of special importance for ecology, agriculture and environmental management. In the analysis of soils and sediments, batch sequential extraction procedures are traditionally used for the fractionation of TM according to their mobility and bioavailability.1–4The nominal “forms” determined by operational fractionation can help to estimate the amounts of TM in different reservoirs which could be mobilized under changes in chemical properties of soil.4,5However, the traditional sequential extraction procedures (SEP) are rather laborious and require at least a few days because in many cases the kinetics of TM recovery from solid samples can be slow. In addition, all SEP are based on a series of batch extraction experiments while naturally occurring processes are always dynamic.An interesting continuous-flow extraction system for the fractionation of TM has been recently proposed.6,7The extraction was performed in a mixing chamber (10 ml volume) closed by a membrane filter while reactants were subsequently passed through. Apart from the simplicity, the system has many other advantages. Disadvantages of the system include the fact that the eluent in contact with the particulate matter is only partially renewed with time and that the flow rate is not stable throughout the experiment.Other techniques employ microcolumns8or microcartridges9filled with dried solid samples. It becomes possible to perform the continuous-flow leaching with on-line determination of elements by inductively coupled plasma mass spectrometry. The proposed method looks very attractive, however, its sensitivity may be somewhat limited by the sample weight (10–80 mg). In contrast to micro techniques, very big columns have been used in hydrogeochemical studies.1010 kg of sample were treated to determine the differences between the binding forms of iron and trace metals in sediments with and without the addition of alkaline substances.11In previous work12we have proposed a new approach to performing an accelerated sequential extraction of TM from environmental solid samples. It has been shown that rotating coiled columns (RCC) earlier used mainly in counter-current chromatography can be successfully applied to the continuous-flow leaching of heavy metals from soils and sediments. A solid sample was retained in the rotating column as the stationary phase under the action of centrifugal forces while different eluents (used according to the Kersten–Foerstner13or McLaren–Crawford14protocols) were continuously pumped through. The developed procedure is time saving and required only 4–5 h, with complete automation being possible. Losses of solid sample were minimal. In most cases a dynamic extraction in RCC provided higher (compared with SEP) recoveries of readily bioavailable and leachable forms of Pb, Zn, and Cd. The Kersten–Foerstner and McLaren–Crawford leaching schemes have been correlated, the former has been found to be preferable.In the present study the applicability of the three-step BCR scheme to the dynamic leaching of TM using RCC will be studied. The extractable contents of TM in reference materials CRM-601 and BCR-701 were certified especially for this scheme15–20adopted by the Standards, Measurements and Testing Program of the European Commission (formerly the BCR Program). Hence, investigating CRM-BCR samples is of special importance for evaluation of the proposed continuous-flow fractionation technique. In addition, some kinetic aspects of continuous-flow leaching in RCC will be considered.