Development of an indirect competitive ELISA for ciprofloxacin residues infood animal edible tissues

An indirect competitive enzyme-linked immunosorbent assay (ELISA) was devel oped to detect ciprofloxacin (CPFX) in food animal edible tissues. CPFX was converted by an active ester method into conjugates CPFX-bovine serum-albu min (CPFX-BSA) and CPFX-human serum albumin (CPFX-HSA), which both allowed production of CPFX-specific rabbit antisera. In the ELISA, CPFX-HSA was coa ted onto the microtiter plate, followed by incubation with standard CPFX an d anti-CPFX antibody. The indirect competitive ELISA revealed that the anti sera have no cross-reactivity with penicillin, gentamicin, neomycin, sulfad iazine, and chlortetracycline. The antisera cross-reacted with enrofloxacin and norfloxacin about 69.8 and 44.6% as much as they did with CPFX. This E LISA was highly sensitive (0.32 ng/mL) to CPFX determination. Recovery of C PFX at 40 mug/kg was 75.58% in pork, 81.29% in chicken, and 84.30% in milk. The coefficients of variation varied from 3.7 to 9.2% over the range of CP FX concentrations studied. The linear detection range was between 1.6 and 1 000 ng/mL. The results suggest that this ELISA is a specific, accurate, and convenient method for the detection of CPFX residues in food animal edible tissues.