Development of an immunoassay for the pyrethroid insecticide esfenvalerate

A competitive enzyme-linked immunosorbent assay was developed for the detec tion of the pyrethroid insecticide esfenvalerate. Two haptens containing am ine or propanoic acid groups on the terminal aromatic ring of the fenvalera te molecule were synthesized and coupled to carrier proteins as immunogens. Five antisera were produced and screened against eight different coating a ntigens. The assay that had the least interference and was the most sensiti ve for esfenvalerate was optimized and characterized. The I-50 for esfenval erate was 30 +/- 6.2 mu g/L, and the lower detection limit (LDL) was 3.0 +/ - 1.8 mu g/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-ba sed. solid-phase extraction (SPE) was used for water matrix. With this SPE step, the LDL of the overall method for esfenvalerate was 0.1 mu g/L in wat er samples.