Elemental screening of plant-based foods by slurry nebulization ICP-MS†
Screening of nutritional and toxic elements in plant-based foods is very important for human health. A reliable solid sampling inductively coupled plasma-mass spectrometry (ICP-MS) method based on the direct introduction of food particle slurries for the simultaneous determination of 16 elements (K, Ca, Mg, Fe, Sr, Zn, Cu, As, Pb, Cr, V, Li, Ti, Rb, Ge, and Ba) was developed. Sample powders were dispersed in 0.5% polyethylene imine by wet-grinding with a tissue cell-destroyer, and 90% of the particles in the slurry were found to be less than 0.8 μm in diameter during the 90 s milling. The feasibility of using direct calibration with simple aqueous standards in slurry nebulization ICP-MS analysis was evaluated by studying the transportation and ionization behavior of particles with different sizes. The upper limits of particle sizes for the efficient transportation and complete ionization were 8.5 μm and 3–4 μm, respectively. In addition, an extended dynamic range technique was developed to simultaneously analyze the major and trace elements in one analysis. Satisfactory recovery (93–106%) and precision (0.3–8.6%, RSD, n = 3) were verified by analyzing a series of food certified reference materials.