Chromium speciation analysis in bread samples.

Chromium is a controversial element with important essentiality and toxicity, depending on its different species; its speciation analysis in principal human foodstuffs, as in the case of bread, is of utmost importance. With this purpose, a method was validated, including a wet acid digestion procedure for total chromium dissolution, a selective alkaline extraction of hexavalent chromium, and ETAAS determination. The method was applied to the determination of total and hexavalent chromium in 152 bread samples. The total chromium contents were 47.3 +/- 20.0 and 50.9 +/- 22.2 microg/kg of dry weight for white and whole bread samples, respectively; those for hexavalent chromium were 5.65 +/- 5.44 and 6.82 +/- 4.88 microg/kg of dry weight. On the basis of a mean daily ingestion of three bread units, the calculated daily intake was up to 12.7 microg/day for total chromium and 1.98 microg/day for hexavalent chromium. Referring to total chromium, bread can contribute up to 10% of the Reference Daily Intake, 120 microg/day.