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Chromium speciation analysis in bread and breakfast cereals


Chromium is highly abundant in the environment both because of industrial use but also natural processes. In the environment it exists mainly in two oxidation states Cr(III) and Cr(VI) which differ with respect to chemical properties and biological activities. While Cr(VI) is recognized as carcinogenic, Cr(III) has been considered to be beneficial for human health for a long time. In more recent time the beneficial effect of Cr(III) has been questioned for healthy people. Anyhow, Cr(VI) should not be present in common food for the health risks accompanied. While the European Food Safety Authority (EFSA) reported that Cr exists in food exclusively as Cr(III), some researchers reported the presence of Cr(VI) in some foodstuffs including bread (see the EVISA news below). We commented that such results call for a validation by highly selective and sensitive analysis. Four years later, a Slovenian group of researchers proved that the reported hexavalent chromium is just an artifact of a technique not sufficiently selective to differentiate between trivalent and hexavalent chromium.

The new study
Even when high performance liquid chromatography is used for the separation of species, Cr speciation analysis is challenged by many error sources. The most critical step for Cr speciation in food by LC-ICP-MS is the extraction of the species from the sample. The problem is related to the incomplete extraction efficiency and the transformation of species during the analysis. In order to address such problems, researchers from France and Denmark optimized the extraction step for bread and breakfast cereals. In order to avoid errors due to species transformation they used species-specific isotope dilution, an approach that can correct for such species transformation during analysis.

Photo: rye bread from Denmark

The method used by them is an adaptation and further development of an approach recently reported for simultaneous speciation analysis of Cr(III) and Cr(VI) in milk and bovine meat samples (Saraiva et al., 2021).  Both species are stabilized during the analytical procedure by complexation. Cr(III) is complexed with EDTA while Cr(VI) is reduced to Cr(III) by 1,5-diphenylcarbazide (DPC) and subsequently complexed by the oxidized form of DPC, namely 1,5-diphenylcarbazone (DPCO). Both complexes are separated by an isocratic ion chromatography system using a short AG7 column. Limits of quantification obtained by the developed method were  14 ng/kg and 47 ng/kg for Cr(III) and Cr(VI) respectively. Cr(VI) was not detected in concentrations surpassing the quantification limit in any of the samples analyzed hence supporting the EFSA statement related to the absence of Cr(VI) in foods, due to the reducing power of such matrices.

The original publication

Marina Saraiva, Petru Jitaru, Jens J. Sloth, Speciation analysis of Cr(III) and Cr(VI) in bread and breakfast cereals using species-specific isotope dilution and HPLC-ICP-MS, J. Food Compos. Anal., 102 (2021) 103991. DOI: 10.1016/j.jfca.2021.103991

Used Instrumentation:

Thermo Scientific - Dionex ICS-5000+
Thermo Scientific - Dionex ICS-6000
Agilent technologies - 7700x ICP-MS

Related studies (newest first):

M. Saraiva, R. Chekri, A. Leufroy, T. Guerin, J.J. Sloth, P. Jitaru, Development and validation of a single run method based on species specific isotope dilution and HPLC-ICP-MS for simultaneous species interconversion correction and speciation analysis of Cr(III)/Cr(VI) in meat and dairy products. Talanta, 222 (2021) 121538. DOI: 10.1016/j.talanta.2020.121538

M. Saraiva, R. Chekri, T. Guerin, J.J. Sloth, P. Jitaru, Chromium speciation analysis in raw and cooked milk and meat samples by species-specific isotope dilution and HPLC-ICP-MS. Food Addit. Contam. Part A, 38/2 (2021) 304–314. DOI: 10.1080/19440049.2020.1859144

  R. Milacic, J. Scancar, Cr speciation in foodstuffs, biological and environmental samples: methodological approaches and analytical challenges - A critical review. TrAC - Trends Anal. Chem., 127 (2020) 115888. DOI: 10.1016/j.trac.2020.115888

B.-H. Chen, S.-J. Jiang, A.C. Sahayam, Determination of Cr(VI) in rice using ion chromatography inductively coupled plasma mass spectrometry. Food Chem. 324/15 (2020) 126698. DOI: 10.1016/j.foodchem.2020.126698

  E.M. Hamilton, S.D. Young, E.H. Bailey, M.J. Watts, Chromium speciation in foodstuff: a review. Food Chem., 250 (2018) 105–112. DOI: 10.1016/j.foodchem.2018.01.016

Fanny Hernandez, Fabienne Séby, Sandrine Millour, Laurent Noël, Thierry Guérin, Optimisation of selective alkaline extraction for Cr(VI) determination in dairy and cereal products by HPIC–ICPMS using an experimental design, Food Chem., 214 (2017) 339–346. doi: 10.1016/j.foodchem.2016.07.099

M.W. Mathebula, K. Mandiwana, N. Panichev, Speciation of chromium in bread and breakfast cereals. Food Chem., 217 (2017) 655–659. DOI: 10.1016/j.foodchem.2016.09.020

  K. Pyrzynska, Chromium redox speciation in food samples. Turk. J. Chem. 40 (2016) 894–905.DOI: 10.3906/kim-1606-5

Véronique Vacchina, Inmaculada de la Calle, Fabienne Séby, Cr(VI) speciation in foods by HPLC-ICP-MS: investigation of Cr(VI)/food interactions by size exclusion and Cr(VI) determination and stability by ion-exchange on-line separations, Anal. Bioanal. Chem., 407 (2015) 3831–3839. doi: 10.1007/s00216-015-8616-3

B. Novotnik, T. Zuliani, J. Scancar, R. Milacic, Content of trace elements and chromium speciation in Neem powder and tea infusions. J. Trace Elem. Med. Biol., 31 (2015) 98–106. doi: 10.1016/j.jtemb.2015.04.003

Shizhong Chen, Shengping Zhu, Yuanyuan He, Dengbo Lu, Speciation of chromium and its distribution in tea leaves and tea infusion using titanium dioxide nanotubes packed microcolumn coupled with inductively coupled plasma mass spectrometry, Food Chemistry 150 (2014) 254–259. doi: 10.1016/j.foodchem.2013.10.150

Breda Novotnik, Tea Zuliani, Janez Scancar, Radmila Milačič, Chromate in food samples: an artefact of wrongly applied analytical methodology?, J. Anal. At. Spectrom., 28 (2013) 558-566. DOI: 10.1039/c3ja30233d

Maria Elisa Soares, Elsa Vieira, Maria de Lourdes Bastos, Chromium Speciation Analysis in Bread Samples, J. Agri. Food Chem., 58 (2010) 1366-13709. DOI: 10.1021/jf903118v

Khakhathi L. Mandiwana, Nikolay Panichev, Svetlana Panicheva, Determination of chromium(VI) in black, green and herbal teas, Food Chemistry 129 (2011) 1839–1843. doi: 10.1016/j.foodchem.2011.05.124

Abayneh A. Ambushe, Robert I. McCrindle, Cheryl M. E. McCrindle, Speciation of chromium in cow's milk by solid-phase extraction/dynamic reaction cell inductively coupled plasma mass spectrometry (DRC-ICP-MS), J. Anal. At. Spectrom., 24/4 (2009) 502-507. DOI: 10.1039/b819962k

Róbert Kovács, Aron Béni, Roland Karosi, Csilla Sógor, József Posta, Investigation of chromium content in foodstuffs and nutrition supplements by GFAAS and determination of changing Cr(III) to Cr(VI) during baking and toasting bread, Food Chem., 105/3 (2007) 1209-1213. DOI: 10.1016/j.foodchem.2007.02.030

Maria E. Soares, Maria L. Bastos, Margarida Ferreira, Selective Determination of Chromium (VI) in Powdered Milk Infant Formulas by Electrothermal Atomization Atomic Absorption Spectrometry after Ion Exchange, J. AOAC International, 83/1 (2000) 220-223.

J. Lameiras, M. Elisa Soares, M. Lourdes Bastos, M. Ferreira, Quantification of total chromium and hexavalent chromium in UHT milk by ETAAS, Analyst, 123 (1998) 2091–2095. doi: 10.1039/a804700f

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last time modified: July 7, 2021


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