ANALYSIS OF THE GRAIN-PROTECTANT PESTICIDES CHLORPYRIFOS-METHYL AND METHOPRENE WITH A 15-MIN IMMUNOASSAY FOR FIELD OR ELEVATOR USE

Antibody-based tests for field use have been developed to enable semiq uantitative analysis of two grain protectants, chlorpyrifos-methyl and methoprene. In these tests, a pesticide-containing methanol extract o f the grain sample and an enzyme-labeled analog of the pesticide are s eparately added dropwise to antibody-precoated test tubes containing a n aqueous diluent. After a brief incubation period, the tubes are rins ed with tap water, and a substrate (chromogen) for the enzyme is added . The color developed is stabilized by acidification. The test result is read either by eye or in a portable field photometer, Pesticide cou ld be extracted efficiently by blending either whole or ground grain f or 1 min using a commercial blender or for 2 min using a probe homogen izer. The overall test time is under 15 min. The assays were sensitive to 0.05 ppm of residue in grain. Also, the results correlated well wi th those obtained using either laboratory immunoassay or chromatograph ic methods.