Determination of Heavy Metal Content in Vegetables and Oils From Spain and Morocco by Inductively Coupled Plasma Mass Spectrometry

Abstract

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.

Keywords:

• Certified reference material
• Heavy metals
• Inductively coupled plasma mass spectrometry
• Oils
• Vegetables

Acknowledgments

This work was supported by Grant D/023185/09 from the Spanish Agency for International Cooperation and Development (AECID), Spain's Ministry of Foreign Affairs. Karima Bakkali is also grateful to AECID for award of a predoctoral grant. The authors would also like to thank the Technical Research Service of the University of Jaén for access to their ICP-MS equipment. Thanks are also due to the staff at the Public Health Laboratory of the Health Council of Jaén and the Animal Production and Health Laboratory of the Andalusian Regional Government (Junta de Andalucía).

Notes

^a r, regression coefficient.

^b LR, linear range.

^c LOD, limit of detection considering the dilution factor.

^d RSD, relative standard deviation (n = 10) for 1 µg/kg.

^e MRL, maximum residue limit (Codex Alimentarius 1995; EEC 2006).

^f Quality criteria (IOC 2009).

^a (±SD, n = 3).

^b Mean information value.

^a (S) Sample from Spain; (M) Sample from Morocco.

^b Sample (S or M) from a hypermarket or supermarket.

^c Sample (S or M) from a fruit and vegetable shop.

^a Sample from southern Spain.

^b Sample from central Spain.

^c Sample from northern Spain.

^a (S) sample from Spain; (M) sample from Morocco.

^b Oil obtained with the traditional method.