QUANTITATION OF BIORESMETHRIN, A SYNTHETIC PYRETHROID GRAIN PROTECTANT, BY ENZYME-IMMUNOASSAY

An enzyme immunoassay was developed for the synthetic pyrethroid, bior esmethrin, by use of a novel approach for synthesis of the pyrethroid- protein hapten conjugate for antibody preparation. Bioresmethrin was h ydrolyzed at the ester linkage, and following protection of the chrysa nthemic acid group, the 2-methylprop-1-ene substituent was oxidatively cleaved. The newly formed and unprotected acid group was reesterified to the other bioresmethrin hydrolysis product [[2-(phenylmethyl)-4-fu ryl]-methanol], and following substitution of the protecting group, th e hapten was coupled to either protein for antibody production or pero xidase for use in the immunoassay. The most sensitive assay employed a n antibody prepared to a derivative with a 4-carbon spacer arm between bioresmethrin and carrier protein, but used a bioresmethrin-enzyme re porter prepared using a 4-(aminomethyl)cyclohexane-carboxylic acid spa cer arm (limit of detection 2 ppb in buffer, 50 ppb in whole wheat or barley grain). Good correlations between HPLC and ELISA determinations of bioresmethrin in whole or ground barley grain were obtained. The s ensitivity of the assay was slightly lower in ground grain or flour mi lling fractions due to interference from coextractives in methanol ext racts. Apart from resmethrin, of which bioresmethrin is the 1R,3R-tran s-isomer, the assay did not detect a variety of other pyrethroids in c ommercial use.