Inorganic elemental compositions of commercial multivitamin/mineral dietary supplements: Application of collision/reaction cell inductively coupled-mass spectroscopy

Thirty five different commercially available multivitamin/mineral (MVM) dietary supplements in tablet, capsule, liquid or powder form for children, women, men, young and adult consumption were analysed by collision/reaction cell ICP-MS for their inorganic elemental compositions including Na, Mg, K, Ca, V, Cr, Mn, Fe, Ni, Cu, Zn, As, Se, Cd, Hg, and Pb. Samples were digested with concentrated nitric and hydrochloric acid (8:2) using a closed vessel microwave system. The validity of the applied method was assessed by the analysis of standard reference materials (SRM 3280, SRM 1566b) and of spiked samples. Special emphasis was given to the percentage deviation of calculated daily intake of each analysed element from their corresponding label claim. Additionally, for toxic elements calculated daily intake values are compared with those of the regulatory guideline values (e.g., recommended dietary allowance). The results revealed that all analysed products have calculated daily intake of As, Cd, Pb and Hg concentrations lower than those of the regulatory limits. The percentage differences between the calculated and claimed daily intake values varied moderately (20%) to significantly (>30%) for the potentially toxic elements, especially Cr, Se, Mn, and Zn. Furthermore, it is not uncommon for the same product to have high, as well as low, elemental compositions compared to their corresponding claimed values.