Determination of pyrethroid insecticide residues in vegetable oils by using combined solid-phases extraction and tandem mass spectrometry detection

A methodology has been developed for the determination of pyrethroid insecticide residues in vegetable oils, based in a solid-phase extraction (SPE) with combined solid supports phases. Several solid phases such as florisil, alumina, C-18 and graphitized carbon black were tested in order to minimize fat residues, being a combination of treated alumina and C18 which provided the best results. Oil samples were partitioned with acetonitrile-hexane (1: 1) and then eluted through a combined column packed with deactivated basic-alumina and C18, employing the acetonitrile extract as elution solvent. Gas chromatography tandem mass spectrometry was used for determination. Tetramethrin, Bifenthrin, Phenothrin, lambda-Cyhalothrin, Permethrin, Cyfluthrin, Cypermethrin, Flucythrinate, Esfenvalerate, Fluvalinate and Deltamethrin were studied. Limits of detection values ranging from 0.3 to 1.4 ng/g and repeatability values from 4 to 13%, evaluated from the relative standard deviation of three analyses of samples spiked at 1 ng/g, were obtained. Neither matrix effects nor interferences were observed employing the proposed treatment in olive oil analysis and recoveries at 25 and 100 ng/g level varied from 104 +/- 2 to 91 +/- 9%. The method can be also used for other vegetable oils such as sunflower, corn and soybean. (c) 2005 Elsevier B.V. All rights reserved.