Determination of various pesticide residues in Greek virgin olive oil by a multiresidue method using different clean up procedures and gas chromatography

The extend use of pesticides, especially insecticides in olive groves consist that the determination of pesticides residues in virgin olive oil is a priority. The main analytical problem is the constitution of the fat matrix that concludes compounds in all range of polarities and interferes with the analysis. This problem is the reason that there are not a lot of reports in bibliography on multiresidue methods for the determination of different chemical families of pesticides in olive oil. In this work a multiresidue method for the determination of 30 insecticides (a triadiazine, 20 organophosphorus, 6 pyrethroids and 3 organochlorines) and 5 herbicides (3 triazines, a phthalic acid and a trifluoromethyl) from different chemical families with various polarities and physicochemical properties is proposed. For the development of the final extraction method three different liquid liquid extraction (LLE) procedures (partition of pesticides between acetonitrile (ACN)-hexane solution of the oil, partition between saturated ACN with hexane-hexane saturated with ACN solution of the oil and partition between ACN-oil) were tested for the optimization of the highest recoveries with the lowest oil residue and a series of experiments for the estimation of of the efficiency of different clean up procedures were performed. LLE extraction of the oil solution in hexane with ACN followed by an ENVI-Carb solid phase extraction (SPE) clean up of the extract gave the best results for the target organophosphorus and triazine compounds determined by gas chromatography using nitrogen phosphorus detector (GC-NPD). For the determination of pyrethroids, organochlorine, phthalic acid and trifluoromethyl compounds by gas chromatography using electron capture detector (GC-ECD), the ACN extract was additionally cleaned throught a Diol-SPE cartridge. The final chosen method gave recoveries between 70-106% and was applied successfully to 27 olive oil samples that cover-all Greek commercial virgin olive oils and olive oils.