Optimization of the liquid-liquid extraction method and low temperature purification (LLE-LTP) for pesticide residue analysis in honey samples by gas chromatography

This work optimized a simple and practical method for identification and quantification of the pesticides chlorpyrifos, lambda-cyhalothrin, cypermethrin and deltamethrin in honey samples. The method was based on liquid-liquid extraction and low temperature purification using acetonitrile: ethyl acetate (6.5 mL:1.5 mL) as the solvent for extraction. A final clean up step with 2 g florisil was performed before analysis by gas chromatography using electron-capture-detector. The technique was proven satisfactory with efficiency exceeding 85% and linear chromatographic response for the tested pesticides, ranging from 0.033 to 1.7 mu g g(-1) with correlation coefficients above 0.99. Detection and quantification limits were lower than 0.016 and 0.032 mu g g(-1) respectively. The proposed method was applied to 11 honey samples. Chlorpyrifos and lambda-cyhalothrin residues were found in two samples at concentrations below maximum residue limit (MRL) established for food products. The presence of these compounds was confirmed by mass spectrometry in SIM mode (GC-MS-SIM). (C) 2010 Published by Elsevier Ltd.