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Sequential Extraction Procedure

June 1st, 2010

By Pradeep Divvela, Project Chemist, Kelso, WA

ShakerSequential extraction is an analytical process that chemically leaches metals out of soil, sediment and sludge samples. The purpose of sequential “selective” extraction is to mimic the release of the selective metals into solution under various environmental conditions.

One commonly used sequential extraction procedure is designed to partition different trace metals based on their chemical nature.

The sequential extraction process is typically accomplished in four (4) steps using:

  1. Acetic acid to extract all exchangeable, acid and water soluble metals
  2. Hydroxyammonium chloride to extract all reducible metals
  3. Hydrogen peroxide to extract all oxidizable metals
  4. Aqua regia to extract all remaining, non-silica bound metals

In each of the steps, calculated concentrations of chemicals and buffers are added and the sample is shaken on an end-over-end shaker. The leachate from each step is then digested and analyzed on an inductively coupled plasma atomic emission spectrometer (ICP/AES) or an ICP/mass spectrometer (ICP/MS), depending on the project requirement.

This multi-step procedure assures that all the metals of concern are completely extracted from the sample. The results from all the different steps are calculated and used to determine the accurate concentrations under different conditions. Factors such as pH of the acid used for adjustment, temperature and duration of extraction are the critical factors that control the concentration of metal extracted from the sample.

Sequential extraction procedure has been extensively studied in the analysis of trace metals including Cd, Co, Cr, Cu, Fe, Mn Ni, Pb and Zn in both river sediments and marine sediments.

Use of total metals concentration as a criteria to assess the potential effects of sediment contamination implies that all forms of metals have equal impact on the environment, which is clearly wrong. Although the total concentration of trace elements in soil gives some indication of the level of contamination, it provides no insight into element bioavailability or mobility. Elements in soils are present in various physicochemical forms, which in turn influence availability. Sequential chemical extraction techniques have been widely used to examine these physicochemical forms, and thus to better understand the processes that influence element availability.


  1. Jennifer M. Jones, Sequential extraction method: a review and evaluation, Environmental Geochemistry and Health, Volume 15, Numbers 2-3, September, 1993
  2. Z.S. Ahnstrom and D.R. Parker, Development and Assessment of a Sequential Extraction Procedure for the Fractionation of Soil Cadmium, Soil Science Society of America Journal 63:1650-1658 (1999)
  3. Shuman, L.M. 1991. Chemical forms of micronutrients in soils. p. 113–144. In J.J. Mortvedt et al. (ed.). Micronutrients in agriculture. 2nd ed. SSSA Book Ser. 4. SSSA, Madison, WI.

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11 Responses to “Sequential Extraction Procedure”

  1. Randy Sherman Says:

    Could you send me a copy of the papers provided in the reference.

    Have you ever seen this method used to demonstrate extraction of metals from solid waste ?

    If so please forward any papers related to use at landfills.


    Also very interesting

  2. Columbia Analytical Says:

    Hi Randy, the references are provided in the article- you may be able to buy copies from the publisher. Also, technical papers do exist that discuss the application of Sequential Extraction for landfills.

  3. Arash Says:

    What is standard method of Selenium measurment?
    Thanks a lot

  4. Columbia Analytical Says:

    Hello Arash, Selenium can be analyzed by ICP-OES (EPA 6010 or 200.7) or ICP-MS (EPA 6020 or 200.8) or GFAAS (EPA 7740) or BRAAS (EPA 7742) instrumentation. Choice of the appropriate analytical technique is governed majorly by the project requirements, sample matrix and detection limits required.

  5. Asowata Timothy Says:

    Guyday, thanks for this pic of imformation. Please can you help forward very recent journals on this process, and journals relating to this method fo polycyclic Aromatic Hydrocarbon. once again thanks, wish to hear frm u soon.

  6. akmal mahazar Says:

    I would like to ask either, there is newer or modified version of SET that currently used. I mean the optimised procedure/technique since I follow the 1983 Badri and Aston, any suggestion?

  7. Lazare Says:

    Hi Pradeep,

    I’m seeking for the updated Zerbe’s method for sequential extraction. Did you hear about that? If so, would you be kind to send a link or a copy of that latest method to me?

    I used that process for my Ph. D. and seeking the following steps.

    kind regards,


  8. Shiva kumar.D Says:

    in between Teiser and BCR procedure for extracting the heavymetals , which is the most accurate protocal?

  9. admin Says:

    Hello Shiva,

    Thank you for your query!

    I am not sure if either the Tessier or the BCR can be considered “more accurate” than the other. The methods are a little different, although they attempt to provide similar characterizations of soil and sediment relative to the behavior of various metals. The “Tessier” procedure utilizes a five-step process to characterize metals (“exchangeable”, “bound to carbonates”, “bound to Fe-Mn oxides”, “bound to organic matter”, and “residual” – i.e. elements typically bound up in the crystalline lattice of the minerals). The BCR is a little different, as it uses a three-step extraction with similar reagents, but not identical (HOAc in the first – apparently combines “exchangeable” + “bound to carbonates”, hydroxylamine hydrochloride in the second – a reducing agent that apparently targets “bound to Fe-Mn oxides”, and hydrogen peroxide in the third – an oxidant that targets “bound to organic matter”).

    Based on the chemistry of the two procedures, they are probably reasonably comparable other than the Tessier differentiates “exchangeable” from “bound to carbonates”. Both use a reducing agent for Fe-Mn Oxide fraction and both use hydrogen peroxide for the Organic fraction. The Tessier includes citrate in the dithionite reagent, which acts as a chelator for certain elements, which could alter results.

    Our laboratory does not have data on hand from comparison studies. A quick search of the internet turned up some publications on both methods, but the ones I accessed did not include comparison studies.

    Thank you,

    Jeff Christian
    Director of Operations, Western USA
    ALS Environmental

    Formerly Columbia Analytical Services, Inc.

  10. Linda Says:

    The BCR Sequential Extraction Procedure was used widely for heavy metal analysis in sludge sample. Generally , the procedures were explained briefly . I can’t find the detail , complete and printed document explaining the BCR Sequential Extraction Procedure .
    where i can get it?

    Kind regards,


  11. oyeudo i p Says:

    In defining the desired partitioning of trace metals, care was taken to choose fractions likely to be affected by various environmental conditions; the following five fractions were selected.
    Fraction 1. Exchangeable. Numerous studies (15-23)
    performed on sediments or on their major constituents (clays, hydrated oxides of iron and manganese, humic acids) have demonstrated the adsorption of trace metals; changes in water ionic composition (e.g., in estuarine waters) are likely to affect sorption-desorption processes.
    Fraction 2. Bound to Carbonates. Several workers (9, 11, 24, 25) have shown that significant trace metal concentrations can be associated with sediment carbonates; this fraction would be susceptible to changes of pH.
    Fraction 3. Bound to Iron and Manganese Oxides. It is well established (26) that iron and manganese oxides exist as nodules, concretions, cement between particles, or simply as a coating on particles; these oxides are excellent scavengers for trace metals and are thermodynamically unstable under anoxic conditions (i.e., low Eh).
    Fraction 4. Bound to Organic Matter. Trace metals may be bound to various forms of organic matter: living organisms, detritus, coatings on mineral particles, etc. The complexation and peptization properties of natural organic matter (notably humic and fulvic acids) are well recognized, as is the phenomenon of bioaccumulation in certain living organisms. Under oxidizing conditions in natural waters, organic matter can be degraded, leading to a release of soluble trace metals.
    Fraction 5. Residual. Once the first four fractions have been removed, the residual solid should contain mainly primary and secondary minerals, which may hold trace metals within their crystal structure. These metals are not expected to be released in solution over a reasonable time span under the conditions normally encountered in nature.
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