ORIGINAL PAPER Quantitation of Metals During the Extraction of Virgin Olive Oil from Olives Using ICP-MS after Microwave-assisted Acid Digestion Eulogio J. Llorent-Martı ´nez • Marı ´a Luisa Ferna ´ndez-de Co ´rdova • Pilar Ortega-Barrales • Antonio Ruiz-Medina Received: 3 February 2014 / Revised: 4 June 2014 / Accepted: 2 July 2014 / Published online: 15 July 2014 Ó AOCS 2014 Abstract Trace metals such as Cu and Fe have negative effects on the oxidative stability of olive oils, and conse- quently, their concentrations are used as quality criterion. Also, maximum levels are established for heavy metals (As and Pb) in olive oils due to their high toxicity. Olive fruits can be contaminated with these metals from soil and air and from the use of pesticides or fertilizers, with the potential contamination of virgin olive oil (VOO) during its extraction from the fruits. This work presents two goals: (a) to optimize an analytical method for the determination of metals in raw olive fruits using an Abencor system; (b) to carry out a preliminary study of the fate of the metals during VOO extraction. The selected metals were quanti- fied in raw olive fruits, and in the olive pomace and VOO obtained after their processing. The metal determination was performed by inductively coupled plasma-mass spec- trometry after microwave-assisted acid digestion with HNO 3 /H 2 O 2 . The results showed that most of the metals (at least 90 %) present in the olive fruits were retained by the olive pomace, so obtaining high-quality VOO from the point of view of its metal content. Keywords Olives Á Olive oil Á Maximum level Á Metal content Á Olive oil production Introduction The Mediterranean diet is a compilation of the nutritional and dietary habits of the countries of the Mediterranean Basin, its principal product being virgin olive oil (VOO), which is a natural oil that preserves the taste, aroma, vitamins, and properties of the olive fruit. It is rich in monounsaturated fatty acids (mainly oleic acid) and con- tains other minor compounds (mainly polyphenols), all of which present important health benefits, including decreased cardiovascular risk factors [1–3]. In the European Union, olive trees are grown in Spain, Italy, Greece, Portugal, France, Cyprus, Slovenia, Croatia, and Malta. Approximately 50 % of the olive groves are located in Spain, with Andalusia representing around 80 % of the VOO production in the country. For Andalusia and similar regions in other countries, VOO commercialization is very important from an economic point of view, so special attention is paid to its quality. Consequently, the International Olive Council (IOC) and the European Union have established quality and purity criteria for each des- ignation (grade) of olive oil, the metal content being one of these criteria. Trace levels of metal ions, such as Fe and Cu, are known to have adverse effects on the oxidative stability of olive oils, therefore, affecting its quality. Other metals, such as As and Pb, are of great interest because of their high toxicity. The IOC has established Maximum Levels (MLs) for the content of As (0.1 lgg -1 ), Cu (0.1 lgg -1 ), Fe (3 lgg -1 ), and Pb (0.1 lgg -1 ) in VOO [4]. The European Union Commission has also established a ML for Pb in VOO (0.1 lgg -1 ) in Regulation (EC) No. 1881/2006 [5]. Several methods have been proposed for the determina- tion of metals in olive oil [6–12] and other vegetable edible oils [8–10, 12–17]. The most widely used detection E. J. Llorent-Martı ´nez (&) Á M. L. Ferna ´ndez-de Co ´rdova Á P. Ortega-Barrales Á A. Ruiz-Medina Department of Physical and Analytical Chemistry, Faculty of Experimental Sciences, University of Jae ´n, Campus Las Lagunillas S/N, 23071 Jae ´n, Spain e-mail: ellorent@ujaen.es 123 J Am Oil Chem Soc (2014) 91:1823–1830 DOI 10.1007/s11746-014-2511-5