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Hexavalent chromium in food ?

(26.04.2015)


Background:
Chromium is one of the most often cited elements when it comes to the point of discussing the necessity of speciation analysis. Chromium mainly exists under two stable oxidation states (Cr(III) and Cr(VI)) which highly differ with respect to chemical properties and biological activities. Whereas Cr(III) is stated to play a role in glucose, insulin, and protein metabolism, hexavalent chromium (Cr(VI)) is mutagenic and carcinogenic.

On their own, such differences justify why the determination of total Cr cannot be used to evaluate the safety of a given sample and why speciation analysis is required for meaningful health risk assessment. For such reason, the presence of hexavalent chromium is regulated in many products (cement, leather, water, ...). However, in foods the interest of Cr(VI) determination still remains under discussion. Mainly two arguments are often used to show that such speciation is pointless. The first one is that Cr(VI) ingested is expected to be reduced in the acidic environment of the stomach. However, during the last 15 years, some studies in animals and humans have shown strong side effects after Cr(VI) oral administration like increased values of urinary Cr or development of tongue and small intestine carcinoma. The second argument is based on the fact that foods from animals or plants origin are considered to be safe since, even if those organisms have been exposed to Cr(VI), they have reduced it to the trivalent form. However, other sources of Cr(VI) than the raw materials have to be considered calling for the testing of its absence.


The new study:
A group of researchers based at Pau (France) now developed a method for the selective chromium speciation analysis of different food items meant to address the major problems:  (i) Cr(VI) concentration is expected to be very low which requires the use of a sensitive and specific analytical tool, (ii) Cr(VI) may react with the ligands present, and (iii) a potential instability of Cr(VI) in the matrix due to the presence of organic matter is able to reduce it. In order to overcome both sensitivity and selectivity issues, the on-line coupling of HPLC with ICP-MS detection was chosen. The ICP-MS was operated in the reaction cell mode with NH3 as the cell gas for reducing potential interferents on chromium.

schemata showing the analytical steps for the determination of Cr(VI) in foods by HPLC-ICP-MS

Foods samples selected and purchased from a local supermarket included dairy products, cereals, chocolate, beverages, vegetables, fruits, eggs, meat and sea products. Chromium was extracted by 10 mL of NH4OH solution (pH 11.5) during 1 h in an ultrasonic bath. For solid samples, the supernatant was separated by centrifugation, ultrafiltered and analyzed by ion-exchange HPLC-ICP-MS. Also the interaction between hexavalent chromium and the food matrix was investigated by size exclusion chromatography using milk as the food  matrix. Evidence was found for the complexation of Cr(VI) potentially present with the ligands. Separation of aqueous phase of the milk (whey) by centrifugation showed that chromium was present in the whey fraction irrespective of the milk origin (cow, goat, infant formula, etc.)

Conditions for ion-exchange chromatography were optimized to separate the chromium signals from interferents. Validation was performed on at least one sample per family of foods by checking the recovery level of a spiked Cr(VI) standard. Good accuracy between 85 and 115% was obtained at two concentration levels 5 and 25 µg/L. Detection limits were between 1 µg/L (for milk) and 10 µg/L (other food samples). Detection limits were in some cases quite close to the total Cr content, but even in the samples with a high Cr content, no Cr(VI) was detected. While total chromium ranged between 4 and 1200 µg/kg, hexavalent chromium was not found in any of the food samples. This absence can be attributed to an instability of Cr(VI) in presence of antioxidants and organic matter in these samples.


The new study:

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


Related studies:

Elsa Vieira, M. Elisa Soares, Marta Kozior, Zbigniew Krejpcio, Isabel M.P. L.V.O. Ferreira, M. Lourdes Bastos, Quantification of Total and Hexavalent Chromium in Lager Beers: Variability between Styles and Estimation of Daily Intake of Chromium from Beer, J. Agric. Food Chem., 63 (2014) 9195-9200. doi: 10.1021/jf502657n

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 Ščančar, 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

Kristin L. Kamerud, Kevin A. Hobbie, Kim A. Anderson, Stainless Steel Leaches Nickel and Chromium into Foods during Cooking, J. Agric. Food Chem., 61/39 (2013) 9495–9501. DOI: 10.1021/jf402400v

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

Maria Elisa Soares, Elsa Vieira, Maria De Lourdes Bastos, Chromium Speciation Analysis in Bread Samples, J. Agric. Food Chem. 58 (2010) 1366–1370. doi: 10.1021/jf903118v

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 (2009) 502–507. doi: 10.1039/b819962k

Estela Figueiredo, M. Elisa Soares, Paula Baptista, Marisa Castro, M. Lourdes Bastos, Validation of an Electrothermal Atomization Atomic Absorption Spectrometry Method for Quantification of Total Chromium and Chromium(VI) in Wild Mushrooms and Underlying Soils,  J. Agric. Food Chem. 2007, 55, 7192-7198. doi: 10.1021/jf0710027

Róbert Kovócs, 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 Chemistry 105 (2007) 1209–1213. doi: 10.1016/j.foodchem.2007.02.030

N. Panichev, K. Mandiwana, M. Kataeva, S. Siebert, Determination of Cr(VI) in plants by electrothermal atomic absorption spectrometry after leaching with sodium carbonate, Spectrochim. Acta Part B 60 (2005) 699–703. doi: 10.1016/j.sab.2005.02.018

Deborah M. Proctor, Joanne M. Otani, Brent L. Finley, Dennis J. Paustenbach, Judith A. Bland, Ned Speizer, Edward V. Sargent, Is Hexavalent Chromium Carcinogenic Via Ingestion? A Weight-of-evidence Review, J.  Toxicol. Environ. Health, Part A, 65 (2002) 701–746. doi: 10.1080/00984100290071018

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

Radmila Milačič, Janez Stupar, Simultaneous Determination of Chromium(i1i)
Complexes and Chromium(v1) by Fast Protein An ion-exchange Liquid Chromatography-Atomic Absorption Spectrometry
, Analyst, 119 (1994) 627-632. doi: 10.1039/AN9941900627


Used Instrumentation and materials:

PerkinElmer ICP-MS (ELAN 6100 DRC II)

Materials used for validation
NRCC TORT-2 (Lobster hepatopancreas)
NIST RM8414 (Bovine muscle)
NIST RM8415 (Whole egg powder)




 Related EVISA Resources

 Link Database: Toxicity of hexavalent chromium (chromate)
Link Database: Human dietary chromium exposure
 Link Database: Industrial Use of chromate
 Link Database: Methods for chromium speciation analysis
Brief summary: ICP-MS: A versatile detection system for trace element and speciation analysis
Brief summary: LC-ICP-MS - The most often used hyphenated system for speciation analysis
Brief summary: Standard methods for chromium speciation analysis
Material Database: Food reference materials





Related information:

EUFIC: Chromium in the diet
NIH: Chromium: Dietary Supplement Fact Sheet
EFSA: Scientific Opinion on Dietary Reference Values for chromium



 Related EVISA News

March 14, 2013: Chromate in food samples: an artefact of wrongly applied analytical methodology
May 23, 2012: EFSA calls for scientific data on chromium speciation and nickel levels in food and drinking water 
April 11, 2012: EPA calls for more study on hexavalent chromium in drinking water
December 27, 2011: EPA ruling on hexavalent chromium in water expected soon 
May 26, 2011: Oral ingestion of hexavalent chromium through drinking water and cancer mortality
November 24, 2010: Deemed Essential to Health for Decades, Chromium Has No Nutritional Effect, UA Researchers Show
October 7, 2010: US EPA offers chance to speak out against hexavalent chromium
November 15, 2009: Hexavalent chromium found in bread
May 17, 2007: Hexavalent Chromium in Drinking Water Causes Cancer in Lab Animals
April 24, 2007: Nutrigenomics: The role of chromium for fat metabolism revisited
June 8, 2006: Scientific journal adds fuel to ongoing chromium debate
November 23, 2004: Chromium (III) - not only therapeutic?

last time modified: May 4, 2015




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