A group of researchers from the Jozef Stefan Institute in Ljubljana (Slovenia) found that former studies indicating the presence of hexavalent chromium in foodstuffs such as tea or bread based solely on the alkaline extraction of chromium are biased. Using a highly selective approach of the hyphenated technique of LC-ICP-MS for chromium speciation analysis they proved that the reported hexavalent chromium is just an artifact of a technique not sufficiently selective to differentiate between trivalent and hexavalent chromium.
Background: 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
