Abstract: A gas chromatography-mass spectrometric （GC-MS） method has been established for the simultaneous determination of 103 pesticide residues in cabbages and apples using programmable temperature vaporizer-based large volume injection (PTV-LVI) and negative chemical ionization (NCI). It was found that much lower detection limits for the investigated pesticides can be obtained. Prior to GC-NCI/MS analysis, the optimized parameters of PTV-LVI were as follows: inlet temperature was set at 45 ℃, split vent flow rate was 20 mL/min, evaporation time was 1 min and evaporation temperature was set at 60 ℃. The volume of injection was 10 μL. Co-extractives were removed from the acetonitrile extracts using solid phase extraction with octadecyl (200 mg) and primary secondary amine (100 mg) sorbents. Matrix matched calibration solutions were used for all the analyses. To evaluate performance of the method, validation experiments were carried out in cabbages and apples at two spiking levels (5 and 10 μg/kg). The average recoveries ranged from 58.5% to 113.2%, and the relative standard deviations (RSDs, n=6) were in the range of 3.3%~14.5%. The limits of detection (S/N=3) were less than 5 μg/kg for all the pesticides. The results show that this method is simple, rapid, sensitive and specific. It is appropriate for the simultaneous identification and quantification of the multi-residues in cabbages and apples.

Key words: apple , cabbage, gas chromatography-mass spectrometry (GC-MS), large volume injection (LVI), multi- pesticide residues, negative chemical ionization (NCI), programmable temperature vaporizer (PTV)