Dear friend, 

I think that Tessier method is good and standard procedure but for further information, I suggest to read this article :

Review Article

Heavy Metal and Trace Metal Analysis in Soil by Sequential Extraction: A Review of Procedures

http://www.hindawi.com/journals/ijac/2010/387803/

Regards 

Thank you Khazaee for your valuable suggestion.

The Tessier and champel method is the widely accepted one. There are several modifications proposed to this method. You can find more information in "Rao, C. R. M., Sahuquillo, A., & Sanchez, J. L. (2008). A review of the different methods applied in environmental geochemistry for single and sequential extraction of trace elements in soils and related materials. Water, Air, and Soil Pollution, 189(1-4), 291-333.

I would like to suggest one more important point. Tessiar method is to be called as Fractionation method rather than speciation method. Because we are separating differerent fractions of the metal, based on solubility. For more information see the attachment.

If you require speciation, then IC with post column derivatization - UV/VIs detection is suitable.

http://www.dionex.com/en-us/products/columns/ic-rfic/transition-metal-packed/ionpac-cs5a/lp-73276.html

If you require speciation, then IC with post column derivatization - UV/VIs detection is suitable.

http://www.dionex.com/en-us/products/columns/ic-rfic/transition-metal-packed/ionpac-cs5a/lp-73276.html

The Tessier sequence has been invented and tested with respective test substances for Zn, Cd, Pb, Cu, Fe. In the early 1980ies, a lot of reports have been issued about. Other elements can be determined as well in the extracts, but the results have to be operationally defined as "mobile in dilute acid" and so on. Pure phosphates do not fit to the sequence. Some sulfides resist oxidation, or get reprecipitated, such as tin. Cr, Fe and Ni are often reprecipitated from salt solutions, and thus their mobility is underestimated.

Please consider, that Co, Ni, Cr, as well as the anions As, Sb, V, P, etc. do not form carbonates under ambient conditions.

A good approach for Interpretation of mobilities is, to adsorb the respective trace elements on your Substrate from tap water, do the subsequent sequential leaching, and see, which fractions have taken the additional amount from the aqueous phase. This depends on the amount of adsorbent phases present. If you are in a limestone area, the Carbonate fraction is clearly not mobile (pH 5 is never reached under ambient conditions), but in igneous rock area, pH 5 is reached at every rainfall event.

Speciation in the liquid Phase is reasonable only, if the extract is about neutral and non-complexing, because this would change the speciation during the leaching process

Dear Ramesh sir,

Thank you very much for giving me valuable insight into the topic.

I agree with Manfred Sager, what you get with the Tessier sequence is information about the reactivity/affinity for the extractant. You define different fractions according to the treatment you applied. Though useful and widely used, the results are different from speciation.

Definitely Tessier method is good and standard procedure. Read the article for more information.

A Review of Sequential Extraction Procedures for Heavy Metals Speciation

in Soil and Sediments

Dear Tiwari sir

Thank you very much for the valuable information

Best

You may read some of my papers about this subject; they may not have reached India yet

M. Sager, R. Belocky, R. Pucsko, Zur Ermittlung der Bindungsformen von Haupt- und Spurenelementen in Sedimenten durch sequentielle Löseverfahren, Acta hydrochim. hydrobiol. 18, 123-139 (1990)

M. Sager, W. Vogel: Heavy metal load of sediments of the River Gurk (Carinthia/Austria) - Merits and limitations of sequential leaching. Acta hydrochim.hydrobiol.21, 21-34 (1993)

M. Sager, Current interlaboratory precision of exchangeable soil fraction measurements, Accred. Qual. Assur. 4, 299-306 (1999)

M. Sager, Speciation of tin in sediments and soils by leaching, Mikrochim. Acta 1986 III, 129-139 

R. Psenner, R. Pucsko, M. Sager, Die Fraktionierung organischer und anorganischer Phosphorverbindungen von Sedimenten - Versuch einer Definition ökologisch wichtiger Fraktionen, Arch. Hydrobiol./Suppl. 70, 111-155 (1984)

The decision between Tessier and BCR depends on your problem. Tessier has 6 steps of sequential extraction whereas BCR relies on 4 steps. So, there is a bit more information at Tessier. Especially the discrimination between the fractions  „water soluble“,„adsorbed“ and „bound to carbonates“ is missing at BCR; it is combined in one step (in the original conception). Both methods were developed to give information on sediments and materials from an oxidizing environment. However, heavy metals in the environment occur in large parts in reducing sediments, along with sulfur and organics. Both methods in their original conception do not adress sulfur at all. Samples from reducing environment will change the bonding forms when handled at ambient conditions (shift of pH). So you have to be thoroughly aware of the sample quality, and not all samples are apt for handling adequate to the method’s capacity the applicability of which should be restricted to materials, soils and sediments from oxidizing environment only. As a control, I would recommend to analyse also S in the extraction solutions (fairly well done by ICP-OES).

Thank you very much Dr. Zachmann.

Yes, I forgot: reducing sediments have to be processed (extracted) under Nitrogen atmosphere in a glove box, because some sulfides (CDs) gest easily oxdized by atmospheric Oxygen.

The BCR-sequence has the Advantage that enough is released in the first step, to stay away from blanks.

The term "plant-available" is rather a philosophy. Which plant, in which period of time ? The roots can take from various chemical species, in different amounts, except from unweathered silicates. Most experiments have been done with cereals. I am currently working with apple trees - this is not so simple.

In a series of aerobic arable soils, the  solubilities of P were much more different in various extracts, then for sulfate (unpublished)

0,01M CaCl2 1:10  P) 2,7 +/- 2,3     S) 8,8 +/- 8,1 mg/kg

0,5M NaHCO3 1:20    57,8 +/- 30,3      30,6 +/- 14,3

0,2M Oxalate pH 3    529 +/- 225         56 +/- 36

The 5-step Tessier et al. method has been successfully used in numerous validated studies for trace metals in soils and sediments, and its popularity has the added advantage of allowing cross study comparisons.  For specific extractions is it is necessary to be sure that the scheme you choose is appropriate for your matrix and target analytes and limits secondary precipitates during the procedure.  For example, some sequential extraction schemes use acid ammonium oxalate to dissolve iron and manganese (oxy)hydroxides, which liberates Pb associated with those phases but can precipitate as insoluble lead oxalate, only to subsequently release in later steps (details in Hayes et al., 2009). 

An unambiguous molecular speciation technique is synchrotron x-ray absorption spectroscopy, i.e. XANES and EXAFS.

Sequential extraction procedures is widely used  for the speciation of heavy metals in  soils.

http://www.uic.edu/classes/cemm/cemmlab/18-1-2010.pdf

Addendum: As pointed out high amounts of heavy metals must be expected from sediments in a reducing environment.Extraction of these materials under ambient conditions will yield  results without relevance. According to Manfred Sager these sediments have to be processed (extracted) under Nitrogen atmosphere in a glove box. However, also sampling in the field and storing of materials must be done under inert conditions (we used Argon). Also extraction solutions used in the glove box must be rinsed free of Oxygen. So in summary, sequential elution of reduced sediments becomes a very intricate job - but in order to get reliable results there is no way to bypass the troubles. 

We described the handling in: "Floodplain lakes as an archive for the metal pollution in the River Elbe (Germany) during the 20th century 

D. W. Zachmann, Andrea van der Veen, Kurt Friese; Applied Geochemistry 06/2013; 35:14-27"