Determination of chlorothalonil in water and agricultural products by a magnetic particle-based enzyme immunoassay

Abstract

A competitive enzyme immunoassay for the quantitation of chlorothalonil in water and agricultural products was developed. This immunoassay utililizes amine-terminated superparamagnetic particles as the solid phase to covalently attach polyclonal rabbit anti-chlorothalonil antisera. Specificity studies indicate that the antibody can distinguish chlorothalonil from its major metabolites and structurally similar pesticides. The immunoassay has a detection limit of 0.07 parts per billion (ppb, ng/mL) in water. The assay compares favorably with GC measurements when water samples are analyzed (r = 0.984). Studies indicate that the assay can potentially be used to analyze agricultural products after homogenization with acetone (detection limit of 20 ppb for celery) or to analyze dislodgable residues after a methanol surface wash (detection limit of 5 ppb for snow pea pods).