Application Of Molecularly Imprinted Solid Phase Extraction For The Analysis Of Food And Environmental Samples

Molecularly imprinted polymers (MIPs) are new polymer materials with specificrecognition ability. In recent years, with the advantages of good selectivity, highadsorption capacity, excellent mechanical stability and chemical stability, MIPs havebeen widely applied in catalysis, chromatographic separation and solid phaseextraction (SPE). MIPs as ideal sorbents in SPE for selective enrichment andpretreatment of target molecules and their structural analogues in complex matrixeshave been developed. Nowadays, the molecularly imprinted solid phase extraction(MISPE) based on traditional solid phase extraction has drawn people’s attention. Inthis thesis, three kinds of MIPs were prepared by suspension polymerization oremulsion polymerization. These MIPs were used as solid-phase extraction sorbentsfor the analysis of antibiotic residues in food and environmental samples. The maincontents of this thesis are as followed:1. Research for the synthesis of magnetic molecularly imprinted polymers (MMIPs)and group-selective of MMIPs for template molecule and structural analogues. TheMMIPs were synthesized by employing sulfamethoxydiazine as template molecule,iron oxide as magnetic core. In the process of synthesis, oleic acid was used to modifythe surface of iron oxide. Then the modified iron oxide was polymerized withassembling solution, generating the MMIPs with core-shell structure. The saturation magnetization (Ms) value of the MMIPs is about16.7emu g-1, which indicates thatthe MMIPs are superparamagnetic. In the extraction process, the MMIPs which wereused as solid-phase extraction sorbents were directly dispersed into environmentalwater for group selective of four sulfonamides and their acetylated metabolites. Whenthe extraction was completed, the MMIPs were separated from environmental watereasily by the application of an adscititious magnetic field, which would facilitate thesubsequent enrichment process. The target analytes were detected by liquidchromatography–tandem mass spectrometry, and the detection limits of the methodare in the range of0.38–1.32ng L-1. The proposed method is suitable for the analysisof environmental water samples.2. The MIPs with high selectivity to florfenicol were successfully synthesized bymicrowave-assisted heating. Compared with traditional hydrothermal method,microwave-assisted heating method can accelerate the polymerization process, greatlyshortening the reaction time. The obtained MIPs were spherical in shape andexhibited a uniform morphology. The analytical method based on the MIPs wasestablished and applied for the determination of the florfenicol in milk. The detectionlimit of the method is4.1ng L-1. The recoveries ranging from91%to94%wereobtained for six milk samples. The results confirmed the practicality and reliability ofthe method.3. The chloramphenicol imprinted polymers were prepared by microwave-assistedheating and applied for the separation of chloramphenicol from honey. Scanningelectron microscopy and Fourier-transform infrared spectrometry were applied tocharacterize the polymers. The binding property and selectivity of polymers wereevaluated and Scatchard analysis was carried out. The polymers with specificselectivity and high affinity to chloramphenicol were successfully applied assolid-phase extraction materials to extract and clean up the chloramphenicol in honey,followed by the LC-MS/MS analysis. The recoveries ranging from87%to93%wereobtained for six honey samples. Furthermore, because of the excellent selectivity, the matrix ef fect of the proposed method was very low.