Journal of Photochemistry and Photobiology A: Chemistry 203 (2009) 1–6 Contents lists available at ScienceDirect Journal of Photochemistry and Photobiology A: Chemistry journal homepage: www.elsevier.com/locate/jphotochem Photodegradation of phytosanitary molecules present in virgin olive oil L. Martínez Nieto a , Gassan Hodaifa b,∗ , S. Rodríguez Vives a , J.A. Giménez Casares a , M.S. Casanova c a Chemical Engineering Department, Science Faculty, University of Granada, 18071 Granada, Spain b Chemical Engineering Department, Chemical Science Faculty, Complutense University of Madrid, Ciudad Universitaria s/n, 28040 Madrid, Spain c Chemical Engineering Department, Environmental and Materials, Experimental Science Faculty, University of Jaén, 23071 Jaén, Spain article info Article history: Received 8 July 2008 Received in revised form 31 October 2008 Accepted 4 November 2008 Available online 14 January 2009 Keywords: Extra virgin olive oil Oil quality Phytosanitary chemicals Photodegradation Kinetics parameters abstract In recent years, traces of active ingredients from phytosanitary products and other products used in treating olive trees have been found in some olive oils because production systems are unable to sep- arate and/or eliminate these chemical residues. Degradation of five phytosanitary chemicals (methyl parathion, ethyl parathion, chlorpyrifos, methyl chlorpyrifos and oxyfluorfen) in virgin olive oil exposed to ultraviolet light at different temperatures has been studied. The influence on the quality parame- ters of treated virgin olive oil and its composition has been analyzed. The photodegradation kinetics can be described by a first-order degradation curve. The half-life values determined at the end of a 150-min UV irradiation (T = 288 K) were as follows: methyl parathion 60.3 min, ethyl parathion 73.0 min, chlorpyrifos 110 min, methyl chlorpyrifos 86.6 min and oxyfluorfen 239.0 min. After the treatment, the phytosanitary chemicals were still present at 19.6, 24.1, 39.1, 32.8, and 67.3% of their initial concentration, respectively. The activation energy for each pesticide was calculated obtaining the following values under the experimental conditions: methyl parathion 15.5 kJ mol -1 , ethyl parathion 29.7 kJ mol -1 , chlorpyrifos 23.5 kJ mol -1 , methyl chlorpyrifos 16.0 kJ mol -1 , and oxyfluorfen 157.9 kJ mol -1 . These results reinforce photodegradation as an effective tool for the degradation of pesticides in olive oil. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Spain is the world’s leading olive oil producer. Olive oil produc- tion has long been a tradition in Mediterranean countries and in recent years these countries have sought to increase its value [1]. The introduction of irrigation, together with the improvement and development of production techniques has tremendously boosted olive-oil production in the past few years. The greater output has led to the development of modern systems for olive harvest and transport and also systems for olive-oil extraction. The use of machines (sweepers, blowers) that facilitate the col- lection of the fallen olives from the ground is the most frequent harvesting practice. However, this system augments the amount of earth accompanying the olives to the mill and thus oil quality seriously declines. In addition, phytosanitary products as insecti- cides, fungicides, and herbicides, are widely used to control pests, diseases, and weeds. It should be noted that each of the active ingre- dients has a safety period (minimum number of days that should elapse between the final application and harvest). Therefore, non- degraded chemical products (phytosanitary not degraded during the safety period) can be persist and pollute not just the water ∗ Corresponding author. Tel.: +34 9139 44115; fax: +34 9139 44114. E-mail address: ghodaifa@quim.ucm.es (G. Hodaifa). but also the soil at harvest time, contaminating the olives that reach the ground. On the other hand, some of the active ingredi- ents of the phytosanitary products are degraded through hydrolytic degradation or photolytic degradation mediated by sunlight. As a result, harmless or harmful residues (phytosanitary residues) can be retained by the ground or leach into the surface water or ground- water. This problem has been discussed during the last decade and was first addressed by analytical studies followed by elaboration of techniques aimed at elimination of phytosanitary contaminants from the water. Nevertheless, this remains a matter of study for researchers worldwide [2] as it is a major problem in many coun- tries. Due to the toxicity of these compounds, the European Union has established guidelines stipulating the acceptable limits for drinking water. The maximum concentrations of phytosanitary residues in drinking water accepted by the European Parliament for the countries of the European Union are 0.1 gL -1 for a given chem- ical and 0.5 gL -1 for the total amount of pesticides [3]. In recent years, there has been remarkable progress in photodegradation of pesticides (as a part of tertiary treatment) since conventional tech- niques of contaminated water treatment were found ineffective. Research results have demonstrated the feasibility of photodegra- dation with UV light on atrazine, isoproturon and mecoprop [4]. The degradation of pentachlorophenol (PCP) has also been stud- ied. Used as fungicide, PCP contains polychlorinated dibenzodioxin (PCDD) and polychlorinated dibenzofuran impurities, which are 1010-6030/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jphotochem.2008.11.025