Preparation Of Novel Polymer Monolithic Materials And Their Application In Sample Pretreatment

As a crucial step in chromatographic analysis, sample preparation is used to convert the target analyte into a suitable form tailored to the instrumental analysis. In recent years, there is a trend to become solvent-free and miniaturization in sample preparation techniques. Solid-phase microextraction (SPME), a solvent-free, small sample consumption and convenient manipulation technique, has been widely applied for sample preparation. Since it emerged in 1990, SPME has gained rapid development in extraction materials and application forms.Because of the simplicity of in situ preparation, well permeability, high phase ratio and good biocompatibility, porous polymer monolith which was a novel structure material has been widely used in sample preparation. However, compare to the commercially polymeric sorbents, the specie and extraction performance of the polymer monolith for SPME has many shortcomings. These problems have shown a heavy effect and restriction on the further improvement of polymer monolith for SPME.The aim of this dissertation is to establish a simple preparation method of polymer monolith; to develop novel polymer monoliths with established method; to investigate the extraction performance of the novel polymer monolith and establish new methods for the analysis of biological fluids and food samples; to develop a new SPME device and enlarge the application range of polymer monolith. The major contents of this dissertation are described as follows:1. A simple and reliable method for polymer monolith preparation was established and proved out by the preparation of poly(2-dimethylaminoethyl methacrylate-co-ethylene dimethacrylate) (DMAE-co-EDMA) and poly(n-dodecyl methacrylate-co-ethylene dimethacrylate) (DoMA-co-EDMA) monolith. Finally, this method was applied for preparation of fourteen different polymer monoliths with polyethylene glycol (PEG) porogenic system.2. A poly(N-isopropylacrylamide-co-ethylene dimethacrylate) (NIPAAm-co-EDMA) monolith was in situ prepared in the capillary and was investigated for in-tube solidphase microextraction (SPME). Factors (ratio between porogens, monomer to crosslinker ratio, total monomer to total porogen ratio, and porogen types) which influence the monolith porous structure were investigated in detail. Investigation of extraction mechanism showed that compounds were adsorbed onto the poly(NIPAAm-co-EDMA) monolith mainly through hydrophobic interaction. Moreover, the extraction medium with a wide range of pH stability exhibited high extraction efficiencies for compounds under highly acidic or basic conditions. Finally, the poly(NIPAAm-co-EDMA) monolithic capillary was successfully applied to the extractions of three tricyclic antidepressants from urine samples.3. A poly(2-acrylamide-2-methylpropanesulfonic acid-co-ethylene dimethacrylate) (AMPS-co-EDMA) monolith was prepared and applied for polymer monolith microextraction (PMME). The effects of several parameters to PMME were investigated, such as pH value, inorganic salt and organic phase concentration of the sample matrix. It demonstrated that the melamine was reserved on the poly(AMPS-co-EDMA) monolith mainly through strong cation-exchange and hydrophobic interactions. A novel approach was presented for determination of melamine in milk products by coupling PMME to high performance liquid chromatography with UV detection.4. A hydrophobic/strong cation-exchange polymer monolith was prepared via a one-step thermally-initiated polymerization method and the preparation conditions were investigated in detail. The resulting poly(2-acrylamide-2-methylpropanesulfonic acid-co-divinylbenzene-co-ethylene dimethacrylate) (AMPS-co-DVB-co-EDMA) monolith has favorable permeability and well mechanical strength. Furthermore, its specific surface area is up to 353 m2/g. The extraction performance of the polymer monolith was evaluated using six antidepressants as model compounds by PMME off-line coupled to HPLC. The results show that the monolith with hydrophobic and strong cation-exchange functional groups exhibits high extraction efficiency towards the antidepressants. Finally, a simple, sensitive, and reproducible off-line PMME and HPLC/ESI-MS methods are described for the determination of ten antidepressants in human plasma.5. Novel stir rod soptieve extraction (SRSE) device has been fabricated, and established a relevant extraction method after the feasibility of applying the SRSE device to sample preparation has been studied. Poly(2-acrylamide-2-methylpropanesulfonic acid-co-octadecyl methacrylate-co-ethylene dimethacrylate) (AMPS-co-OcMA-co-EDMA) monolithic stir rod was used as a extraction medium. An off-line simple method for the simultaneous determination of four tetracycline antibiotics in environmental water samples was developed by coupling SRSE to HPLC with a UV detector; A poly(methacrylic acid-co-ethylene dimethacrylate) (MAA-co-EDMA) monolithic stir rod was prepared and applied for SRSE. A simple, sensitive, and reproducible off-line SRSE and HPLC/ESI-MS methods are described for the determination of four sulfonamide antibacterial residues in milk.