Determination of cadmium, lead, iron, nickel and chromium in selected food matrices by plasma spectrometric techniques

In the frame of a study aimed at investigating the transfer of metal contaminants through the food chain and the effects of food processing, five elements, namely Cd, Pb, Fe, Ni and Cr, were accurately determined in (i) durum wheat grain and derived products, (ii) wheat-based reference materials, (iii) drinking water, used both as an ingredient and for technological purposes in the investigated industrial process. Microwave closed vessel digestion was selected as the dissolution technique for solid samples, whereas water samples were acidified with ultrapure nitric acid and analysed directly. As several analytes had to be quantified at trace or ultratrace levels, inductively coupled plasma mass spectrometry (ICP-MS) was resorted to for analytical determinations. Overall, this straightforward analytical approach enabled to detect the often small changes in element concentration associated with the different technological steps of processing. Nevertheless, detection of heavily interfered elements, especially Cr, as well as analyte quantification at ultratrace-level level in water, posed analytical challenges that required suited analytical solutions.Changes in the sample introduction system and complementary use of inductively coupled plasma atomic emission spectrometry (ICP-AES) straightforwardly overcame the difficulties in determining the analytes in the selected food matrixes. The benefits of ultrasonic nebulization in reducing the effects of problematic spectral interferences were demonstrated. Overall, a robust and high-throughput analytical method was outlined.