Influence of laboratory homogenization procedures on trace element contentof food samples: an ICP-MS study on soft and durum wheat

Sample contamination as a consequence of abrasion of grinding tools during the homogenization of food materials to be analysed for trace elements was addressed. The possible release of 15 trace elements (Al, As, Cd, Co, Cr, C u, Fe, Mn, Mo, Ni, Pb, Se, Sn, V, Zn) from six different grinding and milli ng devices, operating either continuously or discontinuously, was evaluated . All the devices were commercially available and were representative of mo dels usually employed in food and agricultural laboratories. Wheat grains b elonging to one soft and one durum cultivar were used as test material. The determination of the analyte concentrations in subsamples submitted to the different preparation treatments was performed by quadrupole inductively c oupled plasma mass spectrometry (Q-ICP-MS). Accordingly, a suitable digesti on method was developed and the ArC+ interference affecting Cr determinatio n was evaluated and corrected. Statistical differences with respect to the control were detected for 10 elements (Al, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb) and in most cases contamination of the samples was traced back to the c omposition of the grinding equipment. None of the investigated devices was contamination-free with respect to all of the quantified elements. Abrasion of the grinding tools was higher with durum wheat than with soft wheat as a consequence of their different hardness.