Development and Optimization of Immunoassay Method for Detection of Norfloxacin Residues

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.