Development of a bead-based immunoassay for detection of triazophos and application validation

A bead-based competitive fluorescence immunoassay for the detection of triazophos has been developed. In this method, a conjugate of hapten and ovalbumin covalently bound to carboxylated fluorescent bead was used as a coating antigen and goat anti-mouse IgG/R-phycoerythrin conjugate was used as the fluorescent molecular probe. For standards (in 5% methanol in phosphate-buffered saline), the detection range was 0.02–50 ng/ml and the average coefficient of variation (CV) was 8.9%. This bead-assay was highly specific for triazophos, and none of other the structurally similar compounds (diazinon, malathion, parathion and fenitrothion) were recognised (<0.01% cross-reactivity). Vegetable samples (cabbage, carrot, green pepper, spinach, eggplant) were spiked with triazophos in the range of 1.0–100.0 ng/g and analysed by the bead-based immunoassay. The mean recovery and CV were 90.6 and 11.9%, respectively. The results confirmed that the bead-based fluorescence immunoassay is applicable for analysis and quantification of highly hydrophobic pesticide residues in vegetables.