Sequential extraction schemes

Despite the recent efforts for settling operational conditions for metal and metalloid fractionation, conventional batch sequential extraction schemes lack automation and are rather time consuming and laborious. Two additional main problems are the phase overlapping and possible re-adsorption of released elements. 

In the present work it has been shown that on-line coupling of flowthrough fractionation in RCC with ICP-EAS detection enables not only the fast and efficient fractionation of trace elements (TE) in environmental solids to be achieved but allows real-time studies on the leaching process be made. A novel five-step sequential extraction scheme was tested in on-line mode. The optimal conditions for the fractionation were chosen. Investigating elution curves provides important information on the efficiency of the reagents used, the leaching time needed for the separation of each fraction, and the potential mobility of HM forms. 

Hall G.E.M., Gauthier G., Pelchat J.C., Pelchate P., Vaive J.E. Application of a sequential extraction scheme to ten geological certified reference materials for the determination of 20 elements. J Anal At Spectrom 1996 11 787-796. 

Adapted from Nemati K, Baker NKA, Abas MRB, Sobhanzadeh E, Low KH. Comparison of unmodified and modified BCR sequential extraction schemes for the fractionation of heavy metals in shrimp aquaculture sludge from Selangor, Malaysia. Environ. Mont. Assess. 2011 176 313-320. 

The sequential extraction scheme developed by Foerstner [4] was chosen for these investigations except for one modification. In the last step a digestion with aqua regia (German Regulations DIN 38414, part 7) was used. 

The sequential extraction of chromium from soils has been studied [89]. A three-step sequential extraction scheme has been proposed using acetic acid, hydroxylamine hydrochloride and ammonium acetate as extracting agents. Steps 1 and 2 were measured by electrothermal atomic absorption spectrometry (ETAAS). Step 3 was measured by flame atomic absorption spectrometry. Interfering effects when measuring chromium in soils were circumvented through the use of a 1% 5-hydroxyquinoline suppressor agent. 

Single and sequential extraction schemes have been designed in earlier years and widely used to assess the different retention/release of metals in soil and sediment samples (Tessier et al., 1979 Salomons and Forstner, 1980 Thomas et al., 1980 Meguellati et al., 1987). However, the lack of uniformity in the different procedures used did not allow the results to be compared worldwide or the procedures to be... 

The specificity of many of these reagents can be improved by combining a series of them in a sequential extraction scheme in which the residue from a first extraction is used as the material for a second extraction and so on through a number of stages. The soil phase attacked by each extracting reagent is thus restricted by the preceding extraction(s) in the series and is thereby made more specific. 

Marin, B., Valladon, M., Polve, M. and Monaco, A. (1997) Reproducibility testing of a sequential extraction scheme for the determination of trace metal speciation in a marine reference sediment by ICP-MS. Anal. Chim. Acta, 342, 91-112. 

Perez-Cid, B., Lavilla, I. and Bendicho, C. (1996) Analytical assessment of two sequential extraction schemes for metal partitioning in sewage sludges. Analyst, 121, 1479-1484. 

Ure, A.M., Davidson, C.M. and Thomas, R.P. (1995) Single and sequential extraction schemes for trace metal speciation in soil and sediment. Tech. Instr. Anal. Chem., 17, 505-523. 

Table 11.2 Results of chemical equilibrium modelling of the contribution of ferrous iron phases to the proportion of iron (in %) extracted from an anoxic freshwater sediment from the Elbe River near Hamburg (Germany) by the first two acetate buffer steps of a modified Tessier sequential extraction scheme...

Ginepro, M., Gulmini, M., Ostacoli, G. and Zelano, V (1996) Microwave desorption treatment after the oxidation step in Tessier s sequential extraction scheme. Int.J. Anal. 

Fig. 10-1. Sequential extraction scheme (from Farago and Mahmoud, 1983). 

Table 9.5 Extractants and forms of potentially toxic metals (PTMs) separated by various sequential extraction schemes (the number indicates the order of successive steps)...

Because the SEDEX scheme, like all sequential extraction schemes, is operationally defined, it is important to obtain corroborating evidence for the identity of the separately quantified sedimentary phosphorus reservoirs whenever possible. This can be accomplished by analyzing pore-water chemistry and other solid-phase components of the host sediments, and by linking depth profiles of various solutes and components to SEDEX phosphorus profiles. Some of the most elegant and comprehensive work of this type has been done by... 

Figure 2.7 Variation in the saltmarsh sediment concentration of zinc with depth in four fractions, defined according to the sequential extraction scheme of Tessier, Campbell Bisson (1979) as F2, carbonate F3, Fe and Mn oxide and hydroxide F4, organic F5, residual. The location of the profile is Tites Point, Severn Estuary, UK.

TABLE 11.11. Selected Sequential Extraction Schemes Commonly Used for the Fractionation of Particulate-Bound Metal Species (Post-1979) ... 

Roman numerals in parentlieses indicate various stages in the sequential extraction scheme. 

Novel Sequential Extraction Scheme Krishnamurti and Naidu (2000) modified the sequential extraction scheme developed by Krishnamurti et al. 

TABLE 11.13. Multistep Selective Sequential Extraction Scheme for Eractionatlon of Solid Metal Phases... 

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