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

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.