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

A method has been developed for the specific and sensitive determination of Cr(VI) in foods. First, the interactions between Cr(VI) and the matrices were investigated by size-exclusion HPLC-ICP-MS (SEC-ICP-MS). Evidence was found for the complexation of Cr(VI) potentially present with the ligands. For quantification of Cr(VI), the method was based on an alkaline extraction (NH4OH solution at pH 11.5) followed by Cr(VI) determination by anion-exchange HPLC-ICP-MS. Analytical performances of the method were satisfactory in terms of linearity, specificity, accuracy, repeatability, and intermediate precision. Detection limits ranged from 1 to 10 mu g/kg, depending on the matrices investigated. The method was then applied for the determination of Cr(VI) in several products (dairy products, flour, chocolate, vegetables, fruits, meat, fish, eggs, and beverages) from different brands and origins. Cr(VI) was found in none of the samples investigated. To further investigate the reason for this absence, a stability study of spiked Cr(VI) was therefore conducted. A semi-skimmed cow milk was selected for this study. Cr(VI) was shown to be unstable in this matrix with a degradation rate increasing with the temperature.