Abstract: Modified EDC method was employed to synthesize norfloxacin (NOR) artificial antigen and New Zealand rabbits were immunized for anti-NOR polyclonal antibody (pAb) production. An indirect competitive ELISA standard curve was established. The developed assay was sensitive and had a linear range from 0.07 to 31.8 ng/mL (R2 = 0.9627), with IC50 and LOD of respectively 1.5 ng/mL and 0.04 ng/mL. The optimal pH and phosphate ion concentration in assay buffer were determined to be 7.4 mmol/L and 10 mmol/L, respectively, and the concentration adjustments for methanol and NaOH (30 mmol/L) in dilute solutions did not exceed 30% and 10%, respectively. The produced pAb had broad-spectrum specificity and exhibited a high cross-reactivity with ciprofloxacin (83.3%), pefloxacin (78.9%), enoxacin (68.2%), enrofloxacin (51.7%) and lomefloxacin (41.7%). The results obtained suggest that the established icELISA method be used for the multi-determination of fluoroquinolone residues.

Key words: norfloxacin (NOR), fluoroquinolone (FQs), indirect competitive ELISA, multi-residue detection