Multiresidue determination of 156 pesticides in watermelon by dispersive solid phase extraction and gas chromatography/mass spectrometry

Abstract

A rapid multiresidue method was developed for the simultaneous determination of 156 pesticides in commercial watermelon. The method involves a liquid-liquid extraction using acetonitrile coupled with dispersive solid phase extraction cleanup. The extracted elution of pesticides was determined by gas chromatography with electron impact mass spectrometric detection in the selected ion monitoring mode (GCMS-SIM). Standards were prepared spiking blank watermelon samples to counteract the observed matrix effect. The method was validated by fortified at the level 0.020-0.120 mg/kg in watermelon. The average recoveries of all analytes were between 70% and 121%, and standard deviations were below 16%. The limit of quantitation (LOQ) for most compounds was below 0.005 mg/kg, which were lower than the maximum residue levels established by Korean legislations. The proposed method has been applied to the analysis of the 156 pesticide residues in commercial watermelon samples.