Abstract: A time-resolved fluroimmunoassay (TRFIA) for the determination of ciprofloxacin (CPF) in an indirect competitive immunoassay mode was developed and applied. CPF-OVA was coated by physical adsorption onto a microtitre plate, and CPF standard or sample was competed with CPF-OVA for limited anti-CPF antibody, which was traced using europium-labeled goat anti rabbit IgG. The effects of experimental conditions including CPF-OVA concentration, buffer type, and reaction time on the sensitivity of TRFIA were explored. Under optimal conditions, the method revealed a detection limit of 0.5 μg/L, an IC50 of 4.32μg/L and a linear range (IC20－IC80) of 1.13－28.85 μg/L. The spike recovery rates of CPF in honey and milk at three spike levels were in the range of 80.66%－100.30% and 76.30%－95.22%, respectively, and the intra-batch and inter-batch coefficients of variation were 7.42% and 10.92%, respectively. The method was sensitive, specific, stable and suitable to be used for high-throughput determination of CPF residues.

Key words: ciprofloxacin, time-resolved fluroimmunoassay, antibody, recovery