[Two sample pretreatment methods and their applications in the determination of 111 pesticides and related chemicals in aquatic products].

Two sample pretreatment methods were developed and applied to determine 111 residues of pesticides in aquatic products. For Method I, the residues were extracted from homogenized tissue with acetone-ethylacetate-n-hexane (1 : 1 : 1, v/v/v), and then were redissolved in acetonitrile; for Method II, the residues were extracted from homogenized tissue with acetonitrile - water under ultrasonication, and then were separated by liquid-liquid partition. The supernatants were purified using solid phase extraction (Envi-18 and PSA columns) prior to the GC-MS analysis. The determination was performed in selected ion monitoring (SIM) mode with the external calibration for quantitative analysis. Under the optimal conditions, the detection limits (S/N = 3) for residues of pesticides were in the ranges of 0.001 -0.026 mg/kg. The recoveries of Method I for the spiked standards at concentration of 0.25 mg/kg were 72% - 113% with the relative standard deviations (RSDs) of 3.4% - 12.1%. The recoveries of Method II were 51% - 127%, among which the recoveries for 94% pesticides were between 70% and 120% with the RSDs of 3.2% - 13.8%.