DETERMINATION OF ORGANOPHOSPHORUS PESTICIDE-RESIDUES IN FRUITS BY GAS-CHROMATOGRAPHY WITH ITD AND NPD DETECTION

Several widely used organophosphorus insecticides, diazinon, methyl-pa rathion, fenitrothion, malathion, fenthion and methidathion were selec ted for inclusion in this work, A comparative study of the multiresidu e determination of these compounds in citrus fruit and grapes has been carried out by gas chromatography with nitrogen-phosphorus and ion tr ap detection, Samples were spiked with 0.1, 0.5 and 1 mg kg(-1) of eac h pesticide and blended in a Sorvall homogeniser with ethyl acetate. C olumn clean-up on Florisil was necessary for citrus peer extracts, The average recoveries varied from 81 to 107% with a relative standard de viation between 0.3 and 9.5% for GC-ITD and from 86 to 104% with a rel ative standard deviation ranging from 1.4 to 8.0% for GC-NPD. The dete ction limit of the method was 10 ng gl or less for each organophosphor us insecticide, with both detectors. This method was applied to the an alysis of treated lemons and 0.25 mg kg(-1) of fenitrothion in fruit w as detected a week after treatment and identified by its mass spectrum . The results obtained showed that the proposed methods are reproducib le and sensitive enough for the simultaneous determination of these in secticides in fruits at residue level.