Rapid on-site immunoassay for diflubenzuron in grains Original Research Article

An antibody-based test for field use has been developed to enable a screening test for diflubenzuron in animal feed grain. In this test, a pesticide containing methanol extract of the grain sample and an HRP-labeled diflubenzuron derivative are separately added to the antibody-precoated 8-well strip. After a brief incubation period, the strip is washed and a substrate for the enzyme is added. The color development is stopped by acidification, and the test result can be read either by plate reader or a portable field photometer. Diflubenzuron could be extracted efficiently by blending ground grain for 2 min using methanol. The overall test time is around 15 min. The test had a limit of detection of 3 ppb (0.75 ppm in grain) and gave quantitative estimates in the range of 0.75–25 ppm in the grain. No significant matrix effect was observed after methanol extraction of the residue was diluted 1/50 with 1%BSA–PBS. The results correlated well with those obtained using either laboratory immunoassay or HPLC method.