A competitive enzyme-linked immunosorbent assay (ELISA) was developed for the quantitative detection of fenpropathrin [(RS)-α-cyano-3-phenoxybenzyl-2,2,3,3-tetramethylcyclopropanecarboxylate]. Polyclonal antisera were isolated from rabbits immunized with two different fenpropathrin hapten conjugates. One hapten contained an amino function; the other contained a carboxyl group for conjugation to carrier proteins. Mollusk hemocyanins, thyroglobulin, and fetuin were used as carrier proteins. The antisera varied greatly in their affinities for fenpropathrin. A homologous assay system using the coating antigen format was the most sensitive. The IC50 for fenpropathrin was 20 μg/L, and the lower detection limit was 2.5 μg/L. Pyrethroids, such as phenothrin, permethrin, resmethrin, fenvalerate, deltamethrin, cyfluthrin, and cypermethrin, and the pyrethroid metabolites, 3-phenoxybenzoic acid and fenpropathrin acid, did not cross-react significantly in this assay. Ten percent acetone or methanol and a pH of 4 were determined to be optimum assay conditions. Various cationic, anionic, and nonionic detergents had no significant effect on the assay. Keywords: Fenpropathrin; pyrethroid; ELISA; pesticide; enzyme immunoassay; cross-reactivity

A competitive enzyme-linked immunosorbent assay was developed for the detection of the pyrethroid insecticide esfenvalerate. Two haptens containing amine or propanoic acid groups on the terminal aromatic ring of the fenvalerate molecule were synthesized and coupled to carrier proteins as immunogens. Five antisera were produced and screened against eight different coating antigens. The assay that had the least interference and was the most sensitive for esfenvalerate was optimized and characterized. The I(50) for esfenvalerate was 30 +/- 6.2 microg/L, and the lower detection limit (LDL) was 3.0 +/- 1.8 microg/L. The assay was very selective. Other pyrethroid analogues and esfenvalerate metabolites tested did not cross-react significantly in this assay. To increase the sensitivity of the overall method, a C(18) sorbent-based solid-phase extraction (SPE) was used for water matrix. With this SPE step, the LDL of the overall method for esfenvalerate was 0.1 microg/L in water samples.

The pyrethroids are one of the most heavily used insecticide classes in the world. Sensitive and rapid analytical techniques are needed for assessments of human exposure to these compounds. Highly sensitive and selective ELISAs for glycine conjugates of esfenvalerate key metabolites phenoxybenzoic acid (PBA) and s-fenvalerate acid (sFA) were developed. Rabbits were immunized with either N-(3-phenoxybenzoyl)-4-amino-L-phenylalanine-fetuin or N-[(S)-4-chloro-2-(methylethyl)benzeneacetyl]-4-amino-L-phenyla lan ine -fetuin, and all sera were screened against numerous coating antigens. The antibodies with the least interference and best sensitivity were optimized and characterized. The I(50)s for sFA-glycine and PBA-glycine in buffer were found to be 0.40 +/- 0.12 microg/L (1.47 +/- 0.44 nmol/L) and 0.42 +/- 0.18 microg/L (1.56 +/- 0.67 nmol/L), respectively. Both assays exhibited high selectivity. Little or no cross reactivity to the parent compound and other metabolites was measured. The matrix effects of urine were investigated. Solid-phase extraction (SPE) strategies were used in an attempt to decrease the matrix effects and increase the sensitivity of the overall method. The limit of quantitation (LOQ) for both sFA-glycine and PBA-glycine in urine with SPE is 1.0 microg/L (3.70 nmol/L). These assays could be used as markers of exposure for monitoring biological samples.

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