Multi-class multi-residue analysis of pesticides in edible oils by gas chromatography-tandem mass spectrometry using liquid-liquid extraction and enhanced matrix removal lipid cartridge cleanup

Abstract

This study presents the development and validation of a method for the multi-class multi-residue analysis of pesticide residues in edible oils using liquid-liquid extraction followed by EMR-Lipid (enhanced matrix removal - lipid) cartridge cleanup, and then analyzed by gas chromatography tandem mass spectrometer (GC–MS/MS). The method was optimized for analyte recovery, matrix removal, and water removal during the sample extraction, sample cleanup and sample drying steps. The extraction efficiency of lipophilic pesticides (i.e. organochlorine) from the hydrophobic oil matrix was improved using a two-step liquid-liquid extraction with a mixture of ethyl acetate and acetonitrile. EMR-Lipid cartridges provided efficient and selective cleanup of the tested oil matrices. The developed method was verified by analyzing four edible oil matrices: olive oil, corn oil, soybean oil and canola oil. The results demonstrated that the method effectively removes unwanted matrix co-extractives better than conventional PSA/C18 dispersive solid phase extraction (dSPE) cleanup, while still delivering acceptable recovery results (recoveries of 60–120%) for the majority of pesticides tested. With the established quantification method, over 95% of the pesticides obtained for 70–120% accuracy, RSD < 20%, and calibration curves from 1 to 500 (400) ng/g in oil with R2 > 0.99.