Preparation Of Molecularly Imprinted Microspheres For Veterinary Drugs And Their Applications

Veterinary drugs Residues(VDR) could not only cause serious environmental problems, but also be harmful to human health. Detection of veterinary drug residues is an important part of food safety and quality control. Erythromycin (EM) and erythromycin ethylsuccinate (EEs) are macrolides antibiotics which have antibacterial activity on staphylococcus aureus, various streptococci and gram-positive bacteria. However, if the large amount of EM (or EEs) is taken by a person, it could cause nausea, vomiting, diarrhea, abdominal pain, and even the fever, rash and angioneurotic edema. Currently, the methods of detection for EM and EEs often include HPLC, LC- MS and other methods. Moreover, the sample required to be pretreated, such as by solid phase extraction (SPE) and so on. However, the selectivity of traditional solid-phase media (such as C18) was lower, and it usually results in difficult to analysis of those samples' complex compositions.Molecularly imprinted polymers for the target molecule are "tailor-made" polymers which were highly selective to the target molecules. In recent years, molecularly imprinted technology has been widely used in pharmaceutical analysis, environmental monitoring, sensors and other fields. In this study, the preparation of molecularly imprinted polymers and their properties of veterinary drug EM and EEs were studied. The main studies are as follows:1. Preparation of molecularly imprinted microsphere for erythromycinAt present, the preparation of molecularly imprinted polymer for erythromycin has been reported. The preparation method mainly focused on bulk polymerization. The polymers produced by this method were a large of blocks, they need to be ground and sieved before using. This method not only is time-consuming, but also has a poor performance on selectivity and reproducibility. The preparation of molecularly imprinted microspheres for erythromycin with high adsorption capacity and excellent selectivity by aqueous suspension polymerization was presented for the first time, in which erythromycin was used as template molecule, methacrylic acid as functional monomer and ethylene glycol dimethacrylate as cross-linker. Morphological characterization and micropore properties of the imprinted microspheres for erythromycin were assessed by scanning electron microscopy, laser particle size analyzer and pressure mercury analyzer, respectively. The imprinting performance of the imprinted microspheres was evaluated, and selectivity analysis indicated that the imprinted microspheres could specifically recognize erythromycin from its structure analogues. The binding mechanism between erythromycin and methacrylic acid was investigated by UV-Vis spectro-photometry. Furthermore, adsorption kinetics and adsorption isotherm of the imprinted microsphere are employed to investigate the binding characteristics of the imprinted microspheres. Results showed erythromycin can be adsorbed rapidly by the imprinted microspheres, and the maximum static binding capacity is up to 122.78 mg g-1. In addition, the molecular imprinting polymer for erythromycin was used as pre-treatment for actual sample of milk, the results indicated that MIPs have a good selective adsorption capacity, and the recovery rate was up to 90.42%. 2. Preparation of molecularly imprinted microsphere for erythromycin ethylsuccinateSo far, preparation of molecularly imprinted polymers for erythromycin ethylsuccinate has not been reported yet. This is the first time to present the preparation of molecularly imprinted microspheres for EEs by aqueous suspension polymerization. The MIPs were prepared by using EEs as template molecule, methacrylic acid (MAA) as functional monomer, ethylene glycol dimethacrylate (EDMA) as cross-linker. The morphological, particle size and specific surface area of MIPs were characterized by scanning electron microscopy, laser particle size analyzer and mercury analyzer, respectively. The analysis suggested that the diameter of the prepared imprinted microspheres could be controlled within about 60μm. The binding behavior of the template EM on the MIPs was evaluated by UV-Vis spectrophotometric analysis. The results suggested that the optimal ratio of template molecule to functional monomer is 1:6. The selectivity analysis indicated that MIPs had a good selectively adsorption ability to EEs.