GC-MS Determination of Residual Endosulfan and Chlorpyrifos in Aquatic Products

Residual amounts of endosulfan and chlorpyrifos in aquatic products (taking eel as testing sample) were determined by GC-MS with negative chemical ionization (NCl) source.The smashed and slurried sample was extracted with ethyl acetate,and the extract obtained was evaporated to dryness at 40 ℃.The residue was taken up with acetonitrile and purified by passing through the acidic aluminum oxide chromatographic column,and the acetonitrile solution was dried at 50 ℃ by N2-blowing.The dried residue was dissolved in a definite volume of n-hexane and used for GC-MS determination with SIM mode.Ranges of linearity of standard curves for the 3 compounds (i.e.,chlorpyrifos,α-endosulfan and β-endosulfan) found were all in the range of 0.2 μg·kg-1 to 10.0 μg·kg-1.Detection limit (3S/N) of the method was found to be 0.5 μg·kg-1.Values of recovery found were in the range of 81%-95%,and values of RSD′s (n=8) were less than 5%.