The Studies On Preparation And Application Of Molecularly Imprinted Polymers For The Major Abused Drugs In Foods Feeds

Nowadays, the abused drugs in foods and feeds have been strictly banned, and the Maximum Residue Limits (MRLs) were legislated. Hence, new technologies for enrichment and purification of drug residues have aroused increasingly interests in future studies. The solid phase extraction (SPE) and immunoaffinity chromatography (IAC) are now widely used. However, generic sorbents for SPE usually lack selectivity, and are easily subject to interference by non-target substances with similar characteristics. Although IAC is capable of differentially adsorbing target analytes, it still has some disadvantages such as lacking stability and high costs of antibody preparation. The molecularly imprinted solid phase extraction (MISPE) possesses the similar selectivity with the immunoaffinity and better stability and simplicity than it. Hence, MISPE has become the one of the most important applications of MIPs and displayed higher selectivity than conventional SPE with respect to the binding of target analytes from complex matrices.In this study, the developments and applications of MISPE were comprehensively introduced. The molecularly imprinted polymers for reserpine, chloramphenicol and ampicillin were all prepared by non-covalent methods, respectively. Furthermore, the characteristics of these polymers were discussed, and the application of polymers in solid phase extraction was investigated.1. The specific molecularly imprinted polymers (MIPs) of reserpine (RES) using methacrylic acid (MAA) as the functional monomer and its derived MISPE cartridges for purification and enrichment in feeds were developed and characterised in this study. Evaluation of the various polymers by binding assays indicated that the optimum ratio of functional monomer to template was 4:1. Furthermore, the selectivity and enrichment capacity of the MIPs were assessed by the chromatographic method, which demonstrated that the MIPs can be used as alternative separation materials for RES isolation in feed samples at three spiked levels of 0.50, 1.00 and 5.00μg/g, with the recoveries above 80%. Combination of BET analysis, NMR and UV-vis spectroscopy for investigation on the imprinting and recognition properties revealed that the strong specific interactions between the functional monomer and RES in the prepolymerization solutions or the aqueous solutions were probably responsible for RES recognition. These data showed that the developed MISPE can be a valuable tool for the clean-up and enrichment of RES from the feeds.2. The majority of MIPs were synthesised by bulk polymerization, with the process of obtaining the appropriate polymeric particles which requires grinding and time-consuming sieving with low yield. This leads to inconvenience and makes the method not feasible for manufacturing uses. Furthermore, the shapes and sizes of the particles are usually irregular, resulting in high pressure and decrease of selectivity. Hence, to increase the feasibility for MIPMs production and applicability in aqueous samples, we prepared the novel MIPMs against CAP for MISPE analysis by aqueous suspension polymerization, with water as the suspension medium to mimic the natural condition of CAP during the course of polymerization for improving the specificity, and to avoid complicated post-treatment procedures after polymerization. The optimum ratio of functional monomer to template for the specific rebinding of CAP was 4:1. The resulting MIPMs for CAP had the ability to specifically adsorb CAP, and the MISPE based on the MIPMs was shown to be applicable for clean-up and preconcentration of trace CAP in milk and shrimp samples with high recoveries of 92.7% and 84.9%, respectively. A fast accurate and selective analytical method using the MISPE for extraction of CAP in combination with HPLC-MS/MS for analysis has been developed, and the detection limit for CAP in honey residue was 0.1μg/kg.3. In this study, the ampicillin (AMPI) molecularly imprinted polymer microspheres (MIPMs), used as the solid-phase extraction (SPE) sorbents, were first synthesized by aqueous suspension polymerization. Evaluation of the imprinted polymers by chromatographic analysis indicated that the optimum type and ratio of functional monomer to the template was DEAEM and 8:1, respectively. Under the optimal SPE conditions, the spiked AMPI in the honey samples was purified and enriched. The recoveries were all above 89% and the HPLC chromatogram of AMPI obtained before and after SPE treatment obviously showed that the matrix interferences could be almost removed by the washing step, thus achieving substantial improvement on sample preparation for further determination.In conclusion, the MIPs of RES and the MIPMs of CAP and AMPI were first synthesized, and were successively applied for preconcentration and clean-up for the major abused drugs in foods and feeds. Furthermore, the imprinting and recognition mechanism were comprehensively and systematically studied, which could provide a valuable reference for the related basic research and application in practical uses of MIPs against other abused drugs. Finally, the novel MISPE for purification and enrichment toward the corresponding drugs in foods and feeds were developed for determination, with satisfactory recoveries and improved sensitivity.