Development of an enzyme-linked immunosorbent assay for carbaryl

Seven rabbit antisera were obtained by immunization with either N-(1-naphthylacetyl)-6-aminohexanoic acid (3) or 1-(1-naphthyl)-3-(5-carboxypentyl)urea (8) conjugated to keyhole limpet hemocyanin (KLH). From these sera Ab2114 (against 8KLH) was used for the optimization of an enzyme-linked immunosorbent assay (ELISA) for the determination of the insecticide carbaryl. An I50 of 2-5 ng/mL and a detection limit of 0.2 ng/mL were obtained using N-(2-naphthoyl)-6-aminohexanoic acid 5) coupled to conalbumin as a coating antigen. No interference with naphthol, the main degradation product of carbaryl, was observed. An enzyme tracer was prepared by covalently linking hapten 5 with alkaline phosphatase. When the ELISA was performed using a format involving coating the plate with antibodies, an I50 of 0.4-0.6 ng/mL and a detection limit of 0.05 ng/mL were obtained. Preliminary studies with different samples showed that this immunoassay can be used for the determination of carbaryl in water, soil, body fluids, and food samples. This paper demonstrates the flexibility of using stable derivatives of a target compound such as carbaryl to generate antibodies and a sensitive ELISA for molecules containing functionalities susceptible to chemical hydrolysis and biodegradation