New Methods For Determination Of Ofloxacin Residues In Milk

As food safety was attracted more and more attention, the problem of veterinary drug residues has been widely concerned in society and then the analysis and detection technology of the veterinary drug residues has been developed rapidly too. For complex matrices, the detection of trace veterinary drugs requires not only accurate sample preparation methods, but also highly sensitive analysis techniques. This thesis explored the sample pre-treatment and fluorescence spectrophotometry technique to detect ofloxacin residues in milk samples respectively.The main contents include:1. Firstly, the stainless steel fibers were grafted with hydroxy groups by polymerization of dopamine and then modified with methylsilane. Novel temperature-sensitive molecularly imprinted polymers on the stainless steel fiber matrix were prepared using ofloxacin (OFL) as the template, methacrylic acid (MAA) as the functional monomer, N-isopropylacrylamide (NIPAAm) as the temperature-sensitive monomer and ethylene glycol dimethacrylate (EGDMA) as the crosslinking agent. The imprinted polymers were characterized by scanning electron microscopy (SEM), infrared (IR) and nitrogen adsorption, which proved the polymer was successfully synthesized and porous and benefic to the mass transfer. Though static adsorption experiment, adsorption kinetics experiment and selective adsorption experiment, we found that the material had fast mass transfer, excellent adsorption specificity and selectivity to OFL and its structural analogs. Finally, we chose the fibers as adsorbents to concentrate OFL in milk sample and then high-performance liquid chromatography method was set up for the determination. The satisfactory enrichment and recovery was obtained.2. The determination method of ofloxacin (OFL) with Fmoc-L-alanine-OFL system by enhanced fluorescence in milk sample was established. Fmoc-L-alanine (Fmoc-Ala-OH) was an amino acid derivative with specific optical property. The fluorescence of OFL could be increased when it combined with Fmoc-Ala-OH which formed a stabilized fluorescent system. The type of solvent, the pH of the system, and the interaction time were optimized. Under the optimum reaction conditions, the rectilinear calibration curve (R2=0.9975) was obtained in the concentration range0.001～10μg mL-1. The interaction of the two substances was explored by UV-visible spectrophotometer, computer simulation and other techniques. The method was successfully applied to the determination of trace OFL in milk sample with satisfactory results.