GC-MS Determination of Residual Amounts of Dicofol and Pyrethroids in Dried Orange Peel and Its Products

The sample (2.000 0 g) was soaked with water (2 mL or 4 mL), and then was extracted ultrasonically twice, with 5 mL of a mixture of ethyl acetate and hexane (1+1) for 5 min. The combined extract was dried by blowing, and the residue was dissolved with 2 mL of a mixture of ethyl acetate and hexane (1+1). After the solution was purified by oxidization modified multi-walled carbon nanotubes (MWNTs), dicofol and 8 pyrethroid pesticides in the sample were determined by GC-MS. Rtx-1701 capillary column was used as stationary phase for gas chromatography separation. SIM was adopted in MS, and external standard method was used for quantification. Linear relationships between values of peak area and mass concentration of 9 pesticides were found in the range of 0.010-1.0 mg·L^-1, with detection limits (3S/N) in the range of 3.5-6.0 μg·kg^-1. Test for recovery was made by standard addition at 3 concentration levels, giving results in the range of 84.8%-105%, with RSDs (n=6) ranged from 3.1% to 8.2%.