GC Determination of Residual Amounts of 7 Pyrethroid Pesticides in Litchi

GC was applied to the determination of residual amounts of 7 pyrethroid pesticides, i.e. bifenthrin, fenpropathrin, cyhalothrin, cyfluthrin, cypermethrin, fenvalerate and deltamethrin in litchi. The litchi sample was extracted with a mixture of acetone-n-hexane (1+1), and the extract was purified with activated carbon column and neutral alumina column in series. The analytes were separated on DB-35 capillary column and detected by ECD. Linear relationships between values of peak area and mass concentration of the 7 pesticides were kept in the same range of 0.05-0.8 mg·L^-1, with detection limits (3S/N) in the range of 0.005-0.01 mg·kg^-1. Tests for recovery and precision were made by standard addition method at 3 concentration levels of 0.05, 0.1, 0.2 mg·kg^-1, giving values of recovery and RSD's (n=6) in the ranges of 81.0%-104% and 1.7%-5.1% respectively. The proposed method was used to determine bifenthrin in litchi samples, giving results in consistency with values given by the professional standard method.