A fluorescence polarization immunoassay(FPIA) for the determination of salinomycin(SAL) was developed by using anti-SAL monoclonal antibodies(mAb).Fluorescein labeled SAL(tracer) was synthesized by the N-hydroxysuccinimide active ester method and purified using thin layer chromatography(TLC).The developed FPIA for SAL had a dynamic range from 0.60 to 2193 ng/mL with an IC50 value of 33.2 ng/mL and a detection limit(LOD) of 0.08 ng/mL.No significant cross-reactivities were observed with other drugs but 67.6% with narasin. A fluorescence polarization immunoassay (FPIA) for the determination of salinomycin (SAL) was developed by using anti-SAL monoclonal antibodies (mAb). Fluorescein labeled SAL (tracer) was synthesized by the N- hydroxysuccinimide active ester method and purified using thin layer chromatography (TLC). The developed FPIA for SAL had a dynamic range from 0.60 to 2193 ng / mL with an IC50 value of 33.2 ng / mL and a detection limit (LOD) of 0.08 ng / mL. No significant cross-reactivities were observed with other drugs but 67.6% with narasin.