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Chromate in food samples: an artefact of wrongly applied analytical methodology


Chromium is a controversial element with important biological characteristics, depending on its different species. While chromium is considered essential in its trivalent form, the hexavalent species is classified as genotoxic and carcinogenic. The recommended daily intake of Cr(III) in humans is about 100 to 200 mg per day.

Since toxicologist have found that ingestion of hexavalent chromium would be a health risk, the presence of this carcinogen cannot be tolerated in food. However, since Cr(VI) is a strong oxidant, it is well accepted that due to the presence of organic matter, foodstuffs of plant and animal origin cannot contain significant amounts of Cr(VI). Despite such general agreement, several researchers have reported the presence of Cr(VI) in biological materials including food such as tea and bread (see the EVISA News below).

The new study:
Researchers from the Jozef Stefan Institute in Ljubljana (Slovenia) investigated the hypothesis that the reported presence of hexavalent chromium in foodstuff is an artifact of inappropriately applied analytical methodology, lacking the required selectivity to differentiate between the trivalent and hexavalent species of chromium. In these studies the alkaline extraction of Cr(VI) with 0.1 mol L1 Na2CO3 or 0.01 mol L1 NaOH + 0.1 mol L1 NH4NO3 was applied. In order to prove their doubt, they used highly selective speciation analytical technology based on high performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS) that had been validated in previous work.

Samples investigated included the most popular herbal, white, green, red and black teas, and white and wholegrain bread. Species transformation during sample preparation and analysis was monitored by using species-specific stable isotope dilution analysis.

By using this speciation analysis the researchers confirmed that even added Cr(VI) was almost completely reduced during the extraction procedure by the presence of antioxidants in the tea infusion and no Cr(VI) could be found in any of the tea infusions or extractions. Similar results were obtained for white and wholegrain bread.

The authors concluded, that reported presence of hexavalent chromium in tea, bread or plant materials is merely an artifact of inappropriate analytical methodology.

The original study:

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

Related Studies:

Shahryar Abbasi, Atousa Bahiraei, Ultra trace quantification of chromium(VI) in food and water samples by highly sensitive catalytic adsorptive stripping voltammetry with rubeanic acid, Food Chemistry 133 (2012) 1075–1080. doi: 10.1016/j.foodchem.2012.02.003

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

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

 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

 Related EVISA News

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: March 14, 2013


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