An improved dispersive solid-phase extraction clean-up method for the gas chromatography–negative chemical ionisation tandem mass spectrometric determination of multiclass pesticide residues in edible oils

An improved sample preparation using dispersive solid-phase extraction clean-up was proposed for the trace level determination of 35 multiclass pesticide residues (organochlorine, organophosphorus and synthetic pyrethroids) in edible oils. Quantification of the analytes was carried out by gas chromatography–mass spectrometry in negative chemical ionisation mode (GC–NCI-MS/MS). The limit of detection and limit of quantification of residues were in the range of 0.01–1 ng/g and 0.05–2 ng/g, respectively. The analytes showed recoveries between 62% and 110%, and the matrix effect was observed to be less than 25% for most of the pesticides. Crude edible oil samples showed endosulfan isomers, p,p′-DDD, α-cypermethrin, chlorpyrifos, and diazinon residues in the range of 0.56–2.14 ng/g. However, no pesticide residues in the detection range of the method were observed in refined oils.