Abstract: A gas chromatography-triple quadrupole tandem mass spectrometry (GC-QqQ-MS/MS) with multi-reaction monitoring (MRM) was developed for the simultaneous analysis of 33 pesticide residues in grapes, based on the fragmentation mechanism and mass spectrometric behavior of fragment ions from target compounds. The stable isotope dilution method was applied for quantification. The sample pretreatment involved extraction with acetonitrile by homogenization followed by sequential clean-up on C18 solid phase extraction (SPE) cartridge and tandem aminopropyl and activated carbon SPE cartridges. The results indicated that the calibration curves had a good linearity within the concentration range of 0.001 6– 0.320 0 mg/L with correlation coefficients (R) greater than 0.994 7. The limits of detection (LODs) were 0.064–40.000 μg/L and the limits of quantification (LOQs) were 0.000 02–0.013 33 mg/kg. The recoveries ranged from 70.1% to 120.6% for all target pesticides with relative standard deviation (RSD) less than 17.9%, when spiked at three different concentration levels. The developed method was sensitive and accurate for simultaneous and fast determination of trace or ultratrace pesticide residues in grape and other fruit and vegetable samples. Moreover, the characteristics of pollution and distribution of these pesticides in grape samples from different places in Hunan province, China were discussed by partial least square-discriminant analysis (PLS-DA). The results demonstrated that pesticides against grape grey mold or downy mildew, such as iprodione, azoxystrobin and dimethomorph, were found to be major chemical pollutants in grape samples.

Key words: pesticide residue analysis; grape; stable isotope dilution; internal standard; gas chromatography-triple quadrupole tandem mass spectrometry