ANALYSIS OF THE SYNTHETIC PYRETHROIDS, PERMETHRIN AND 1(R)-PHENOTHRIN, IN GRAIN USING A MONOCLONAL ANTIBODY-BASED TEST

A monoclonal antibody generated to the synthetic pyrethroid-related hapten, (3-phenoxybenzyl)-2,2-dimethylcyclopropane-1,3-dicarboxylate-protein conjugate, was used to develop assays for determination of permethrin and 1(R)-phenothrin in wheat grain and flour milling fractions. The earlier 3-h assay was simplified using two approaches. The antibody was directly conjugated to the enzyme horseradish peroxidase (HRP), which removes a separate incubation and washing step from the assay. Also, an assay has been developed using microwell-bound monoclonal antibody and a HRP-labeled 3-phenoxybenzoic acid derivative. These assay formats have advantages in increased sensitivity and, in the case of the latter assay, accuracy with grain and flour samples. The most sensitive assay format could detect 1.5 ng/mL permethrin; 50% inhibition of antibody binding occurred at 10 ng/mL. These values corresponded to 75 and 500 ppb, respectively, in the original wheat sample. Methanol was the most effective pyrethroid extractant. Use of a simple cleanup procedure for ground grain extracts improved ELISA accuracy but could be omitted for screening purposes.