Abstract: A method for the simultaneous determination of six pesticides in adzuki beans by high performance liquid chromatography-electrospray ion trap tandem mass spectrometry was developed and evaluated. The sample was extracted with 0.1 mol/L NH4HCO3 (pH 5)-methanol (70∶30, v/v). The extract was partitioned with dichloromethane, and cleaned up with gel permeation chromatography. The separation was performed on an Inertsil ODS-3 column (150 mm×2.1 mm, 5 μm) with the gradient elution of methanol and 1% acetic acid as mobile phase. The identification and quantification were performed by electrospray ion trap mass spectrometry with selected ion monitoring mode. The calibration curves of imidazolinone herbicides showed good linearities in the range of 10-200 μg/L (5-100 μg/L for imazaquin) with the correlation coefficients between 0.9987 and0.9997. The limits of detection ranged between 0.2 μg/kg and 0.5 μg/kg (S/N=3). The average recoveries of six imidazolinone herbicides spiked in adzuki beans ranged between 81.6% and 99.4%(n=6) with the relative standard deviations of 3.1%-7.8%. The method has been used for the determination of 6 imidazolinone herbicides simultaneously in adzuki beans with easy operation, high accuracy and good precision.

Key words: adzuki beans , imidazolinone herbicides, liquid chromatography-tandem mass spectrometry （LC-MS/MS）, multiresidue determination, gel permeation chromatography