Monoclonal Antibody-Based Fluorescence Polarization Immunoassay for Furazolidone in Feed

A rapid, specific, and sensitive fluorescence polarization immunoassay (FPIA) method was developed to detect residues of furazolidone, a forbidden drug in feed. An immuno-hapten was designed for monoclonal antibody preparation. Furthermore, seven novel tracers were synthesized and the “heterology tracer” could improve the sensitivity of FPIA significantly. An optimized FPIA method was established with a cross-reactivity of less than 0.1%, IC50 of 5.5 ng/mL. The limits of detection (LOD) calculated from feed samples were 0.5–0.9 ng/mL. Recoveries of fortified samples at levels of 5, 20, and 50 ng/mL ranged from 79.0% to 85.0%. The coefficients of variation were less than 12%.