Fluorescent Determination Of Doxycycline Residue And Preparation Of Molecular Imprinted Solid Phase Extraction Column

Residues of veterinary drugs in animals can enter the human body through the enrichment of food chain, leading to the drug resistance of various pathogenic bacteria, the disorders of intestinal flora, cell canceration, hormone disorders, and other hazards to human health. Therefore, developing the method of extraction and detection of veterinary drug residues in animal food is important for food safety. Doxycycline is a tetracycline antibiotics, used to prevent the bacterial infections in respiratory, digestive and urinary tract in clinic veterinary. In many countries,doxycycline residues in animal food are limited. The methods of detection and extraction of doxycycline are studied in this paper.1. The C₁₀^- phenolic hydroxyl group and C12- enoyl group of tetracyclines can react with Mg2+ at complex ratio of 2:1 and form hyperfluorescence chelate, whose fluorescence can be futher increased in the micellar solution of cetyltrimethyl ammonium bromide. When these are combined with the features of derivative synchronous fluorescence spectrometry such aslarge information and good selectivity, the selective detection of doxycycline can be realized. A new assay is developed to determine the doxycycline residue on the basis of this principle. Under the optimum conditions, the linear dynamic range is 0.2-10 mg/L; the relative standard deviations are between 0.9% and 3.9%; detection limit is 12μg/kg; recoveries of spiked sample are between 90.5% and 107.3%. This method can be used to determine doxycycline residues in pork and the result is satisfactory.2. The molecular imprinted polymers recognizing DC can synthesized when DC is used as template molecule, methylacrylic acid as functional monomers, tetrahydrofuran as solvent,ethylene glycol dimethyl diacrylic ester as the crosslinker, azobisisobutyronitrile as initiator. Optimized synthesis conditions are as follows: the molar ratio of template, methylacrylic acid and ethylene glycol dimethyl diacrylic ester is 1:8:40; reaction temperature is 55℃; and reaction time is 24 h. The adsorbability of the molecular imprinted polymer to template produce from two different affinity binding sites. And molecular size and shape serve as the main factors for the specific affinity of the synthesized polymer.3. The cartridge of DC molecule imprinted solid phase extraction can be prepared through filling the molecular imprinted polymer of DC into it. The extraction condition of the cartridge is optimized. The recoveries of DC can be up to 90.1% when deionized water is used as sample solvent, 2 mL acetonitrile as washing solvent and 20 mL mix solution of methanol:water=9:1 (V/V) as elutriant. The cartridge can be applied to extract and enrich doxycycline from pork samples, and the average recovery of samples spiked at six different levels is 82.4%...