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Chemical process to separate iron oxides particles in pottery sample for EPR dating

dc.contributor.authorWatanabe, S.
dc.contributor.authorFarias, T. M. B.
dc.contributor.authorGennari, R. F.
dc.contributor.authorFerraz, G. M.
dc.contributor.authorKunzli, R. [UNESP]
dc.contributor.authorChubaci, J. F. D.
dc.contributor.institutionUniversidade de São Paulo (USP)
dc.contributor.institutionUniversidade Estadual Paulista (Unesp)
dc.date.accessioned2014-05-20T15:31:52Z
dc.date.available2014-05-20T15:31:52Z
dc.date.issued2008-12-15
dc.description.abstractAncient potteries usually are made of the local clay material, which contains relatively high concentration of iron. The powdered samples are usually quite black, due to magnetite, and, although they can be used for thermoluminescene (TL) dating, it is easiest to obtain better TL reading when clearest natural or pre-treated sample is used. For electron paramagnetic resonance (EPR) measurements, the huge signal due to iron spin-spin interaction, promotes an intense interference overlapping any other signal in this range. Sample dating is obtained by dividing the radiation dose, determined by the concentration of paramagnetic species generated by irradiation, by the natural dose so as a consequence, EPR dating cannot be used, since iron signal do not depend on radiation dose. In some cases, the density separation method using hydrated solution of sodium polytungstate [Na(G)(H(2)W(12)O(40))center dot H(2)O] becomes useful. However, the sodium polytungstate is very expensive in Brazil: hence an alternative method for eliminating this interference is proposed.A chemical process to eliminate about 90% of magnetite was developed. A sample of powdered ancient pottery was treated in a mixture (3:1:1) of HCI, HNO(3) and H(2)O(2) for 4 h. After that, it was washed several times in distilled water to remove all acid matrixes. The original black sample becomes somewhat clearer. The resulting material was analyzed by plasma mass spectrometry (ICP-MS), with the result that the iron content is reduced by a factor of about 9. In EPR measurements a non-treated natural ceramic sample shows a broad spin-spin interaction signal, the chemically treated sample presents a narrow signal in g= 2.00 region, possibly due to a radical of (SiO(3))(3-), mixed with signal of remaining iron [M. lkeya, New Applications of Electron Spin Resonance, World Scientific, Singapore, 1993, p. 285]. This signal increases in intensity under -gamma-irradiation. However, still due to iron influence, the additive method yielded too old age-value. Since annealing at 300 degrees C, Toyoda and Ikeya IS. Toyoda, M. Ikeya, Geochem. J. 25 (1991) 427-445] states that E '(1)-signal with maximum intensity is obtained, while annealing at 400 degrees C E'(1)-signal is completely eliminated, the subtraction of the second one from 300 degrees C heat-treated sample isolate E'(1)-like signal. Since this is radiation dose-dependent, we show that now EPR dating becomes possible. (C) 2008 Elsevier B.V. All rights reserved.en
dc.description.affiliationUniv São Paulo, Inst Fis, BR-05508090 São Paulo, Brazil
dc.description.affiliationUNESP, Presidente Prudente, Brazil
dc.description.affiliationUnespUNESP, Presidente Prudente, Brazil
dc.description.sponsorshipFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
dc.description.sponsorshipConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
dc.description.sponsorshipCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
dc.description.sponsorshipCTR (Technological Center of Radiation)
dc.format.extent1261-1265
dc.identifierhttp://dx.doi.org/10.1016/j.saa.2008.03.034
dc.identifier.citationSpectrochimica Acta Part A-molecular and Biomolecular Spectroscopy. Oxford: Pergamon-Elsevier B.V. Ltd, v. 71, n. 4, p. 1261-1265, 2008.
dc.identifier.doi10.1016/j.saa.2008.03.034
dc.identifier.issn1386-1425
dc.identifier.urihttp://hdl.handle.net/11449/40894
dc.identifier.wosWOS:000261249100015
dc.language.isoeng
dc.publisherPergamon-Elsevier B.V. Ltd
dc.relation.ispartofSpectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy
dc.relation.ispartofjcr2.880
dc.relation.ispartofsjr0,648
dc.rights.accessRightsAcesso restritopt
dc.sourceWeb of Science
dc.subjectDatingen
dc.subjectEPRen
dc.subjectChemical treatmenten
dc.subjectBrazilian ceramicen
dc.subjectICP-MSen
dc.titleChemical process to separate iron oxides particles in pottery sample for EPR datingen
dc.typeArtigopt
dcterms.licensehttp://www.elsevier.com/about/open-access/open-access-policies/article-posting-policy
dcterms.rightsHolderPergamon-Elsevier B.V. Ltd
dspace.entity.typePublication
unesp.campusUniversidade Estadual Paulista (UNESP), Faculdade de Ciências e Tecnologia, Presidente Prudentept

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