Determination of 19 organophosphorus pesticide residues in garlic using solid-phase extraction and gas chromatography-tandem mass spectrometry

A method was developed for determination of 19 organophosphorus pesticides in garlic using solid-phase extraction (SPE) and gas chromatography-tandem mass spectrometry (GC-MS/MS). The pesticides were extracted with V(acetic acid):V(ethyl acetate)=1:99, and then cleaned up on a carbon/NH2 SPE column. The extracts were determined by mode of multiple reaction monitoring (MRM) of GC-MS/MS using external standard method quantification. The linearity range of the method between 0.04 mg/L and 0.8 mg/L was satisfying and the limit of quantitation (LOQ) of all pesticides were low than 0.01 mg/kg. The recoveries of all pesticides at the spiked level of 0.01 to 0.2 mg/kg in garlic matrices were in the range of 68.0% to 130%, with relative standard deviations (RSDs) less than 15.6%. It is demonstrated that this method is sensitive with low background, showing its potential inanalysis of organophosphorus pesticide residues in garlic.