Analytical Methods Determination of the antiradical properties of olive oils using an electrochemical method based on DPPH radical Ioana Vasilescu a , Sandra A.V. Eremia a,⇑ , Camelia Albu a , Antonio Radoi b , Simona-Carmen Litescu a , Gabriel-Lucian Radu a a Centre of Bioanalysis, National Institute of Research and Development for Biological Sciences – Bucharest, 296 Splaiul Independentei, 060031 Bucharest, Romania b National Institute for Research and Development in Microtechnology (IMT-Bucharest), 126A Erou Iancu Nicolae, 077190 Bucharest, Romania article info Article history: Received 7 November 2013 Received in revised form 26 February 2014 Accepted 8 June 2014 Available online 16 June 2014 Keywords: 2,2 0 -Diphenyl-1-picrylhidrazyl Differential pulse voltammetry Olive oils Tocopherols Vitamin E abstract The present work describes the development of an electrochemical method based on the use of 2,2 0 -diphenyl-1-picrylhidrazyl free radical (DPPH Å ) for the determination of the antiradical properties of several olive oils. Differential pulse voltammetry was used as measuring technique while the electrochemical process was recorded at a platinum screen-printed working electrode. The decrease in 2,2 0 -diphenyl-1-picrylhidrazyl peak current intensity was measured at a specific potential value of +160 mV vs. screen-printed pseudo-reference electrode, in the presence of a-, d- and c-tocopherol and olive oil samples, respectively. The obtained results using differential pulse voltammetry, as detection technique for real samples analysis, showed a satisfactory agreement with those obtained by high- performance liquid chromatography coupled with fluorescence detection. The reported electrochemical method is rapid and easy to use, feasible and accessible to be used as an alternative to 2,2 0 -diphenyl- 1-picrylhidrazyl spectrophotometric based method. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction There is a plethora of reports attesting that the traditional Mediterranean diet consisting of fruits, vegetables, cereals, fish and olive oil, due to their content in active principles represents the key to a healthy life. An example supporting this idea is related to the incidence of cancer and cardiovascular diseases that is lower in Mediterranean neighbouring countries with respect to Northern European countries (Cioffi et al., 2010). Olive oil, one of the basic components of Mediterranean healthy diet, is characterised by unique flavours, depending on its native region. The major constituents of olive oil are the fatty acids and triacylglycerols, approximately 95%, while minor constituents are tocopherols, polyphenols, hydrocarbons, sterols and volatile compounds (Ibáñez, Hurtado Benavides, Señoráns, & Reglero, 2002). The minor olive oil constituents are those giving the oil its flavour and proper- ties. The polyphenols are thought to be potential scavengers of superoxide anions and to prevent LDL oxidation (Ruiz-Canela & Martínez-González, 2011). Among the contained tocopherols in olive oils, a-tocopherol is present in higher amounts while c- and d-tocopherols are found in lower quantities (Cunha, Amaral, Fernandes, & Oliveira, 2006). Vitamin E refers to eight major naturally occurring fat-soluble compounds, namely four tocophe- rols (a, b, c and d) and four tocotrienols (a, b, c and d). All the iso- forms have a chromanol ring with a hydroxyl group that is able to reduce free radicals as well as a hydrophobic side chain. The differ- ence between the isoforms consists in the position of the methyl group on the chromanol ring (Fuchs et al., 2003). The oils tested in our work belong to the extra virgin olive oil and to the olive–pomace oil classes, according to the International Olive Oil Council classifications of olive oil as virgin olive oil, refined olive oil, olive oil, and olive oil–pomace oil. The codex standard for olive oils and olive pomace oils (CODEX STAN 33-1981) states that there are allowed the additions of a-tocopherols to these products in order to restore the natural content lost by refining. However the final a-tocopherol concentration should not exceed 200 mg/kg. According to CODEX STAN 33-1981, the virgin olive oil is the oil obtained from the fruit of the olive tree (Olea europaea L.) by mechanical or other physical treatment usually under thermal conditions without any other treatment. During the last years tocopherols attracted much of attention due to their antioxidant properties as well as other nutraceutical effects. In the particular case of antioxidants the dose–effect corre- lation is not necessarily a linear one. Consequently the assessment of both quantitation and effect of antioxidant compounds are equally important when discussing the food beneficial/healthy action. Therefore there is need of developing simple, low cost, user http://dx.doi.org/10.1016/j.foodchem.2014.06.042 0308-8146/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel./fax: +40 21 220 09 00. E-mail address: sandraeremia@gmail.com (S.A.V. Eremia). Food Chemistry 166 (2015) 324–329 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem