New Analytical Methods For The Determination Of Metronidazole In Milk And Honey Samples

Metronidazole （MNZ） is a nitroimidazole derivative and has been used to treatdiseases caused by bacterium and anaerobic protozoan infections. It has also beenused as a promoter to induce the growth of cattle, pigs, poultry, and to improve feedefficiency. However, MNZ is now believed to possess teratogenic, carcinogenic,mutagenic and genotoxic side effects. The irrational use of metronidazole in feed maycuase residue of veterinary drug in food-producing animals which is harmful tohuman. Therefore, the development of accurate, sensitive, and rapid methods fordetecting MNZ is crucial for human food safety. In this paper, based on surfacemolecular imprinting technique, a core-shell magnetic nanoparticles withsurface-imprinted polymer was prepared. The as-prepared imprinted polymer hasbeen successfully applied to the solid phase extraction and electrochemical sensing ofMNZ, respectively.（1） Core-shell magnetic nanoparticles with surface imprinted polymer coating asa new adsorbent for solid phase extraction of metronidazole in food samples. We haveprepared a nanoparticle-based metronidazole-imprinted polymer by combining asurface molecular imprinting technique with a sol-gel process. Metronidazole wasused as a template,3-aminoprophyltriethoxysilane as the functional monomer, andtetraethyl orthosilicate as the cross-linker. The resulting magnetic molecularlyimprinted polymer was characterized by Fourier transform infrared spectroscopy,powder X-ray diffraction, and scanning electron microscopy. The adsorbent can beapplied to the solid phase extraction of MNZ and exhibits high adsorption capacity,good selectivity, favorable reusability, and the feature of magnetic separation. Thematerial was successfully applied to solid phase extraction of metronidazole, followedby spectrophotometric determination in food samples. Spiked recoveries range from88.5%to97.0%with the relative standard deviations （RSDs） of <3.5%in milk samples, and of85.6%to96.0%with RSDs of3.3%-4.5%in honey samples.（2） A core-shell surface molecularly imprinted polymer grafted onto a magneticglassy carbon electrode as a selective sensor for the determination of metronidazole infood samples. The core-shell metronidazole-magnetic molecularly imprinted polymer（MMIP） was synthesized and then attached to the surface of magnetic glassy carbonelectrode （MGCE） with the help of magnetic force in order to prepare MMIP/MGCEsensor. The performance of the obtained imprinted sensor was investigated by cyclicvoltammetry and electrochemical impedance spectroscopy. Various factors, known toaffect the response behavior of the MMIP/MGCE electrode, were studied andoptimized. In comparison with the nonimprinted one, the imprinted sensor exhibitshigh recognition ability and affinity for MNZ and also shows good stability andacceptable reproducibility. Under the optimal experimental conditions, the currentresponse of the electrochemical sensor was linear to MNZ concentrations in the rangefrom5.0×10^-8to1.0×10^-6mol/L and1.0×10^-61.0×10^-4mol/L, The detection limitwas1.6×10^-8mol/L. The method was successfully applied to the analysis of MNZ inmilk samples and honey samples with acceptable recoveries of93.5%to102.2%.