Pesticides in essential oils: Occurrence and concentration in organic and conventional orange essential oils from eleven geographical origins.

In this paper is described for the first time the application of both gas chromatography-tandem mass spectrometry (GC-MS/MS) and ultra performance liquid chromatography-quadrupole-time of flight-mass spectrometry (UPLC-QTOF-MS) to the determination of 75 priority pesticides in orange essential oils (EOs). The sample preparation consisted in a 10-fold dilution of orange EO followed by a direct injection for GC-MS/MS technique and a freeze-out step in the case of UPLC-QTOF-MS analysis. The analytical methods were validated using the SANCO criteria and gave reporting limits (RLs) of 10 μg L-1, 25 μg L-1, 50 μg L-1 and 100 μg L-1 for 57, 13, 4 and 1 pesticides, respectively. The analysis of four others EOs in the context of a proficiency test demonstrated very good performance and versatility of the methods with a detection rate of 100%, 97.8% of correct quantifications and no false negative. Then 49 orange EOs of known origin and quality were analysed using the standard addition procedure. It enabled to highlight significant matrix effects leading to differences in response factor up to 9.0 in GC-MS/MS and 53.1 in UPLC-QTOF-MS, between an orange EO sample to another. It was found that a conventional EO contained on average 17 pesticides for a total concentration of 5.1 mg L-1. Up to 29 different pesticides, 39 in the case of a concentrated EO, were detected in one sample and the sum of the concentration reached 51.1 mg L-1. Regarding the organic samples, none were free of pesticides but the contamination was found to be clearly lower than in conventional EOs. It was found that an organic orange EO contained on average 4 pesticides for a total concentration of 0.087 mg L-1.