Column Extraction for the Determination of Multi-residual Pesticides in Crops and Dixoins in soils

Homogenized samples of crops with different content of water were mixed respectively with Celit-545,anhydrous sodium sulfate,florisil and silica gel to form free-flowing powder samples. Each powdered sample was packed in a column and eluted with solvents of differend polarity. Most eluates could be analyzed chromatographically without further cleanup.Any one of the chosen dispersion agent oould be used for the determination of pesticide residues in crops if polar solvent such as ethyl acetate is utilized in elution.Rereveries of carbamaus,pyrethroid and organophosphorous and organochloro pesticides from some grains,vegetables and fruits and PCDDs from soils were higher than 80%.It has been proven both theoretically and practically that the column extraction method saves time and reagents and simplifies the cleanup proceure.