DETERMINATION OF HEAVY METAL CONTENT IN VEGETABLES AND OILS FROM SPAIN AND MOROCCO BY INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY

An optimized inductively coupled plasma mass spectrometry method was used to analyze trace metals (As, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Sb, and Sn) in vegetable and oil samples. Prior to analysis, the samples were accurately weighed into a Teflon digestion vessel and the metals extracted from their matrix by using nitric acid and hydrogen peroxide in a closed-vessel digestion system. The proposed method is sensitive, with limits of detection between 5 and 38 ng/kg, and precise, with relative standard deviations from 2.8 to 6.1%. In order to verify its accuracy, the method was used to analyze the Standard Reference Materials NCS ZC85006 Tomato and Certified Used Oil HU-1. The method was successfully applied to the comparative determination of residues of the studied metals in vegetable (tomato, pepper, onion, spinach, lettuce, carrots, and marrow squash) and oil samples (virgin olive, maize, sunflower, and olive pomace) from Spain and Morocco. The results obtained revealed that the contents in metal residues depend on the particular type of food and its origin, probably due to the different production, processing, storage, and preservation methods.