Photodegradation of phytosanitary molecules present in virgin olive oil

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 separate 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 parameters 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.