The Molecular Imprinting Technique Applied Research In The Residues Of Veterinary Drugs Tetracycline Antibiotics

Molecularly imprinted polymers (MIPs) are chemically systhetic functional polymeric materials that have biomimic properties. The imprinting process is performed by co-polymerising functional and cross-linking monomers in the presence of a template molecule. The subsequent removal of the imprint molecule reveals binding sites in the polymer network, which are complementary to the template in size and shape. That allows the highly specific rebinding of the template. Furthermore, usually MIPs are reusable, need low cost of preparation, exhibit a high mechanical and chemical stability and are applicable to a vast amount of operating conditions. In this paper, a molecularly imprinted polymer was prepared by bulk polymerization using tetracycline as template. It was used as solid phase extraction sorbent and a simple, rapid and specific HPLC method was developed for the quantitative analysis of tetracyclines (OTC, TC, CTC) in pork and milk samples. The thesis is divided by three chapters, as described below:ChapterⅠThe developing history, the basic principle of molecularly imprinting technology and the preparation techniques were firstly reviewed. The influence on the selectivity of MIP is then described and the methods to evaluate the MIP were also discussed. The application in environmental determination for tetracyclines and the trends for molecular imprinted technology were summarized in the last.ChapterⅡMolecularly imprinted polymers (MIPs) with tetracycline as template were prepared by bulk polymerization and precipitation polymerization. The adsorption/desorption kinetics of TCs on MIPs and NIPs were investigated, and MIPs were proved to have higher selectivity for TCs than NIPs. The Scatchard analysis for MIPs was consisted of two linear parts. It might be concluded that the binding site configuration could be classified into two different specific binding properties. TC-MIPs were compared with templated materials obtained by conventional bulk polymerization. SEM reviewed that the microsphere polymers exhibited a regular spherical shape with a high degree of monodispersity to the corresponding bulk polymers. The influence of the type and amount of functional monomer, the type and amount of cross-linker, polymerization temperature, porogen, and the ratio of template molecule and functional monomer to cross-linker on the size of the obtained particles were investigated. UV–Vis spectrophotometer experiments revealed that the microsphere polymers provided higher affinity to the template in contrast to imprinted polymers prepared by bulk polymerization.ChapterⅢTC-MIPs were used as molecularly imprinted micro-solid-phase extraction (MIMSPE) procedure for the selectively preconcentration of tetracyclines from pork and milk samples. A molecularly imprinted solid phase extraction (MISPE) coupled with HPLC method was developed to detect tetracyclines in pork and milk. Various parameters for the extraction efficiency of the MISPE have been evaluated. After 30 mL pork tissue and milk extracts (blank and spiked) were loaded onto the cartridges, the cartridges were washed with 10 mL water. Than 8 ml of methanol was used as elution. The mobile phase of the HPLC system was methanol: buffer (0.1 M malonate, 0.05 M magnesium chloride, pH 6.5 with NH3?H2O) (30:70, v/v) at the flow rate of 1 mL min-1. The column temperature was 40 oC. Detection wavelength was set at 355 nm. The linear ranges for three TCs were 0.10-5.00 mg L-1 and detection limits were within the ranges of 0.05-0.14 mg L-1. Three TCs were detected directly in non-spiked samples. The recoveries of oxytetracycline, tetracycline, and chlortetracycline in the spiked pork meat and milk samples were 72.7–79.4%, and 73.6–80.1%, respectively. This method has been successfully applied to preconcentrate and determine of tetracyclines in animal food samples directly.