Highly sensitive enzyme-linked immunosorbent assay for chlorpyrifos. Application to olive oil analysis.

Highly sensitive enzyme-linked immunoassays for chlorpyrifos, one of the most applied insecticides, are presented. Several haptens were synthesized for immunoreagent production and ELISA development. The best immunoassays obtained are based on an indirect coated-plate immunoassay format. Two assays were optimized; one shows a limit of detection of 0.3 ng L-1, an I50 of 271 ng L-1, and a dynamic range between 4 and 16 474 ng L-1. The other one has a limit of detection of 0.07 ng L-1, an I50 of 7 ng L-1, and a dynamic range between 0.4 and 302 ng L-1. The assays were used to quantify chlorpyrifos in olive oil using a simple and rapid sample extraction procedure. The good recoveries achieved in both assays (109% mean value) and the agreement with values given by the GC reference method (110% mean value) indicate their potential for either screening or laboratory quantification. Keywords: Organophosphorus pesticides; chlorpyrifos; ELISA; olive oil