Determination of Norfloxacin in Food by Capillary Electrophoresis Immunoassay with Laser-Induced Fluorescence Detector

A simple and sensitive capillary electrophoresis immunoassay method with laser-induced fluorescence detector was developed for the determination of norfloxacin in food samples. The assay was based on the competitive immunoreaction between fluorescein isothiocyanate-labeled norfloxacin tracer and free norfloxacin with a limited amount of antinorfloxacin antibody. In this study, the experimental parameters affecting the norfloxacin determination were systematically optimized including incubation time, buffer pH and concentration, and separation voltage. Under the optimal conditions, norfloxacin could be accurately quantified within 3 min using Na2B4O7/NaH2PO4 buffer (30 mmol/L, pH 8.0) for background electrolyte and 25 kV for the separation voltage. The linear range of the method was 0.08-50 mu g/L with a detection limit of 0.005 mu g/L. The relative standard deviations for migration time and peak area of the immunocomplex were 0.17 % (intraday) and 3.46 % (intraday), respectively. The proposed method has been further applied to the determination of norfloxacin in milk, chicken, pork, and fish samples, exhibiting satisfactory recovery and sensitivity. These results indicated that the proposed method might serve as an efficient tool for the selective determination of norfloxacin in food samples.