MATRIX SOLID-PHASE DISPERSION EXTRACTION PROCEDURE FOR MULTIRESIDUE PESTICIDE ANALYSIS IN ORANGES

A multiresidue extraction method based on matrix solid-phase dispersio n (MSPD) is optimized for the extraction and gas chromatographic scree ning of eighteen insecticides (aldrin, carbophenothion, captafol, chlo rpyriphos, chlorfenvinphos, diazinon, dicofol, alpha-endosulfan, beta- endosulfan, ethion, fenitrothion, folpet, methidathion, malathion, met hyl-azinphos, methyl-parathion, phosmet, and tetradifon) from oranges. After optimization of different parameters, such as type of solid pha se used and the amount of solid phase or eluent, recoveries ranged fro m 67 to 102% with relative standard deviations ranging from 2 to 10%. The limits of detection, calculated as 3 times the baseline noise rang ed from 2 to 171 mu g/kg. These limits of detection were about 10 time s lower than the maximum residue levels established by the European Co mmunity. Compared with classical methods, the described procedure is s imple, less labour intensive and does not require preparation and main tenance of equipment. Troublesome emulsions, such as those frequently observed in liquid-liquid partitioning did not occur.