Inductively coupled plasma mass spectrometry with on-line leaching to assess the maximum bio-accessibility of toxic and essential elements in wheat from Saudi Arabia

Abstract

For the first time, a continuous leaching method, coupled on-line with inductively coupled plasma mass spectrometry (ICPMS), was used on wheat samples to assess the maximum bio-accessibility of several trace elements. This technique involves the sequential continuous leaching of a mini-column of sample by artificial saliva, gastric juice and intestinal juice, while the effluent from the mini-column flows to the nebulizer of an ICPMS instrument. A larger mini-column than previously used with this method was utilized to improve reproducibility. The results of the continuous on-line leaching method were comparable to those of a conventional batch method despite the fact that it requires 15 min as opposed to several hours by the batch method. They show that bio-accessibility varies from element to element between samples. The bio-accessible fraction of the majority of elements (e.g. As, Fe, Ni, Cu, etc.) was mostly released by saliva and gastric juice. Particular attention was paid to Cd and Pb in wheat, because even a portion of these elements being bio-accessible could have major implications for consumers. The highest bio-accessible concentrations of Pb were found to be 780 ± 90 μg kg⁻¹ and 890 ± 100 μg kg⁻¹ for Safeer wheat and Qassim wheat, respectively, corresponding to 60% and 100% bio-accessibilities. Furthermore, the maximum Cd bio-accessible concentration was 1810 ± 280 μg kg⁻¹ for Qassim wheat samples, corresponding to 100% bio-accessibility, which is a concern for consumption by children.