A novel chemiluminescence assay of organophosphorous pesticide quinalphos residue in vegetable with luminol detection

BACKGROUND Organophosphorous pesticides are the most popular pesticides used in agriculture. As acetylcholinesterase inhibitors, organophosphorous pesticides are toxic organic chemicals. The control and detection of organophosphorous pesticide residue in food, water, and environment therefore plays a very important role in maintaining physical health. A sensitive, rapid, simple chemiluminescence(CL) method has been developed for the determination of quinalphos based on the reaction of quinalphos with luminol-H2O2 in an alkaline medium. The method has been applied to detection of quinalphos in vegetable samples with satisfactory results. RESULTS The CL method for the determination of organophosphorous pesticide quinalphos is based on the phenomenon that quinalphos can apparently enhance the CL intensity of the luminol-H2O2 system. The optimal conditions were: luminol concentration 5.0 x 10-4 mol/L, H2O2 concentration 0.05 mol/L.pH value 13. In order to restrain the interference from metal ions, 1.0 x 10-3 mol/L of EDTA was added to the luminol solution. The possible mechanism was proposed. CONCLUSION Under the optimum reaction conditions, CL was linear with the concentration of quinalphos in the range of 0.02 mug/mL -1.0 mug/mL and the detection limit was 0.0055 mug/mL (3sigma). This method has been successfully applied to the detection of quinalphos in vegetable samples. According to the experimental data, the average recoveries for quinalphos in cherry tomato and green pepper 97.20% and 90.13%. Meanwhile, the possible mechanism was proposed.