Development of a sensitive ELISA for the analysis of the organophosphorous insecticide fenthion in fruit samples

Two fenthion haptens, 4-(4-(dimethoxyphosphorothioyloxy)-2-methylphenylamino)-4-oxobutanoic acid (H1) and 6-(methoxy(4-(methylthio)phenoxy)phosphorothioylamino)hexanoic acid (H2), were synthesized. H1 was conjugated with bovine serum albumin (BSA) and H2 with ovalbumin (OVA) by the active ester method. Then H2-OVA conjugate was used as coating antigen, while H2-BSA conjugate was used to produce polyclonal antibodies. After optimization, an effective competitive indirect enzyme-linked immunosorbent assay (ELISA) for determination of fenthion was established with the new combination of antibody/antigen, I50 of which was 0.01 ng/ml, and there was only cross reactivity (CR) with fenitrothion (4.5%), and CRs with other tested pesticides were all below 0.1%. The recoveries obtained by standard fenthion addition to the different fruit samples such as grape, peach, pear and tomato were all from 79.8% to 106.0%. Therefore, the optimized ELISA may become a new convenient and satisfied analytical tool for monitoring fenthion residues in agricultural samples.