Development of a broad-selective immunoassay for multi-residue determination of type II pyrethroids in West Lake water

With the purpose of finding an immunoassay of similar sensitivity for type II pyrethroids such as fenpropathrin, cypermethrin, deltamethrin, esfenvalerate, cyhalothrin, fluvalinate and flucythrinate, we prepared three kinds of polyclonal antibodies (Pabs), and screened against nine coating antigens (CAgs). The final selected antibodyantigen combination based on heterologous assay was further optimised and tested for tolerance to methanol concentration, ionic strength and pH changes. Sensitivity of optimal immunoassay was found to be quite similar among cypermethrin, deltamethrin and esfenvalerate, as IC50 values were 23.2, 24.5 and 25.1 mu g/L for the three pyrethroids, respectively. No cross-reactivity was measured to type I pyrethroids or other relative metabolites. This immunoassay was used to detect different combinations of cypermethrin, deltamethrin and esfenvalerate spiked in West Lake water, and recoveries were between 95.6% and 103.6%, which indicated that the chosen ELISA was feasible for multi-residue analysis.