Abstract: 【Objective】Quinolones and gentamicin are highly effective and broad-spectrum antibacterial drugs. They have significant antibiotic effects on gram-negative and gram-positive bacteria, and are widely used in agriculture in China. Because these two types of drug residues in foods of animal origin may cause harm to human health, therefore, in order to protect the consumers’ health, it is necessary to develop a detection method for simultaneous monitoring these two types of drugs residue level in food. A colloidal gold immunochromatographic method was developed for the simultaneous detection of 13 quinolones and gentamicin residues in milk.【Method】In this study, based on the quinolones and gentamicin monoclonal antibodies, the colloidal gold particles were prepared by sodium citrate reduction method, and mixed labeled with same ratio of these two types of monoclonal antibodies. The effect of pH and antibody amount for gold-antibody conjugation on the strip test sensitivity was investigated. Meanwhile, the coating condition of these two types of antigens was selected. A colloidal gold rapid test strip was developed to simultaneously detect 13 quinolones and gentamicin residue in milk on these bases, and the test strip using the principle of direct competition.【Result】The results showed that the method can simultaneously detect 13 quinolones and gentamicin. These 13 quinolones include enrofloxacin, ciprofloxacin, norfloxacin, flumequine, pefloxacin, ofloxacin, enoxacin, oxolinic acid, marbofloxacin, fleroxacin, orbifloxacin, danofloxacin and lomefloxacin. The test strip has no cross-reaction to other quinolones such as sarafloxacin, difloxacin, sparfloxacin and pazufloxacin, etc. At the same time, it has no cross-reaction to other aminoglycosides such as streptomycin, neomycin and kanamycin, etc. The limit of detection was estimated to be 20 ng·mL^-1 in milk for both the 13 quinolones and gentamicin, since the detection test line on the strip test completely disappeared at this concentration. The detection limit for milk sample of these two types of drugs fully meets the detection limit requirements of China. Samples were detected directly without treatment, and the entire testing process was completed within 5 min.【Conclusion】A parallel analysis of quinolones and gentamicin in 60 blind raw milk samples conducted by HPLC-MS/MS showed comparable results to those obtained from the strip test. All positive samples were detected while false positive and false negative phenomenon did not appear with this screening method. The results demonstrated that the developed method is suitable for the onsite determination of quinolones and gentamicin residues in a large number of samples. Since this method provides only qualitative and semiquantitative results, the determined positive samples should be further confirmed by more sensitive methods such as HPLC-MS/MS.

Key words: quinolones, gentamicin, residue, colloidal gold immunochromatographic