RAPID GC-MS DETERMINATION OF RESIDUAL PYRETHROID PESTICIDES IN VEGETABLES AND FRUITS

The sample solution of vegetable or fruit was prepared by treating the sample (20 g) through the following steps:disintegration of sample;extraction with methyl cyanide;evaporation of an aliquot of the methyl cyanide extract on a water bath at 80 ℃ to nearly dryness;taking up the solution with n-hexane and passing the solution through florisil column;evaporation of the eluate,on a water bath at 55 ℃ with blowing of nitrogen,to nearly dryness;diluting of the solution to 2.0 mL with n-hexane;filtration with 0.45 μm filtermenbrane and sampling for GC-MS determination.The selected ion mode and the mass selective detector were applied in the GC-MS analysis,eliminating effectively the matrix interferences.The residual pesticides were characterized,both qualitatively and quantitatively,according to the retention time and the abundance of characteristic ion.Recoveries were found to be in the range of 75%-108%.RSD′s were less than 10%.Limit of detections were in the range of 0.000 90-0.008 4 mg·kg-1.