Rapid on-site immunoassay for diflubenzuron in grains

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 1150 with 1%BSA-PBS. The results correlated well with those obtained using either laboratory immunoassay or HPLC method. (C) 2002 Elsevier Science B.V. All rights reserved.