Further method development and improvement of the accuracy of rapid test kits for pesticide residue analysis
2001
Calumpang, S.M.F. (Philippines Univ. Los Banos, College, Laguna (Philippines). National Crop Protection Center) Morillo, G.G.L. | Flavier, M.E. | Quintana, B.B.
The trials were aimed at increasing the sensitivity, versatility, coverage and usefulness of the National Crop Protection Center (NCPC) rapid test kits (RTKs) for analyzing selected insecticides in fruit and root vegetables by developing color charts, factoring-in weight correction values for samples, changing the extracting solvent, and testing the kits in analyzing contents of commercial insecticide formulations. Semi-quantitative color detection limits (color charts) of selected organophosphate, carbamate and pyrethroid insecticides were developed using the appropriate NCPC RTKs. The organophosphate insecticide methamidophos displayed a blue color. The carbamate insecticides exhibited various colors: blue by carbaryl, violet by carbofuran, a stable pink spot by BPMC, and an orange spot by methomyl, unusual for a carbamate. The pyrethroid insecticides, deltamethrin and cypermethrin, were both violet under ultraviolet radiation. Cyfluthrin and methiocarb could not be detected at the levels tested. The minimum and maximum detection limits were 0.05 and 0.7 ug for methamidophos, 0.05 and 0.9 ug for both carbaryl and carbofuran, 0.05 and 0.6 ug for BPMC, 1 and 10 ug for methomyl, and 0.05 and 0.7 ug for both cypermethrin and deltamethrin. The weight correction factor (WCF) specific for eggplant, tomato, potato, radish, bitter gourd, cucumber and carrot was determined. It was established that without the WCF, a gross overestimation of residue levels could occur and this might give rise to problems in the field. The current commercial NCPC RTKs use acetone as extracting solvent. It was established that ethyl acetate was superior to acetone in extracting from cabbage the following insecticides: chlorpyrifos, diazinon, malathion, methamidophos, triazophos, carbaryl and profenofos. Residues in cabbage present at the maximum residue limits, ranging from 0.1 to 8 mg/kg, could be detected without having to concentrate the extract by heating. Methods were also developed to other insecticide residues (carbaryl, fenvalerate, and deltamethrin) present at CXL levels in stored products such as rice, corn and mungbean. Data showed that with the RTKs, rapid assessment of insecticide formulations can be done to determine quality of formulated products in the field in case of doubt
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