Analysis of 20 trace and minor elements in soy and dairy yogurts by ICP-MS

The content of 20 trace and minor elements in soy and dairy yogurts consumed in Spain has been determined using inductively coupled plasma-mass spectrometry (ICP-MS) after microwave digestion. This work presents two goals: a) to determine the nutritional value in terms of minor elements content, using recommended daily allowance data; b) to determine the levels of trace toxic elements and compare them with the acceptable daily intake values. The developed analytical method was validated by using both milk certified reference materials and recovery experiments over different yogurt samples, obtaining satisfactory results in all cases. In addition, a comparison between the levels of minor elements found in soy and dairy yogurts was performed. Much higher concentrations of Cu and Mn were found in soybean products (up to 30-fold higher) and minor differences were observed in the content of Fe and Zn. Other minor element found at higher concentrations in soy yogurts was Ni (effect usually observed in plant-origin foods), which was determined at levels up to 450 ng g(-1) in some samples. Finally, the levels of toxic elements were very low, even below the detection limit in some cases. (C) 2011 Elsevier B.V. All rights reserved.