| Recently, the sample pretreatment techniques develop fast, and attract more and more attentions. Although lots of advanced analytic instruments are developed to detect biological samples, environmental samples and drug, also the process of sample pretreatment is necessary in order to satisfy the demand of Chromatography/Mass detection. Traditional sample pretreatment containing ultrasonic extraction, reflux extraction, fiber-coated solid phase micro-extraction and so on is tedious and time-consuming, and sometimes it is not accurate for quantity. So it is very important to explore and develop fast, convenient, accurate and reliable sample pretreatment methods.This dissertation mainly developed and studied two kinds of sample pretreatment methods, that is microwave-assisted extraction and solid phase extraction based on magnetic materials. It contains the extraction of catechin and epicatechin from green tea and the extraction of chlorogenic acid from tobacco residues by microwave-assisted extraction technology; and considering about the advantage of magnetic micro-/nano-material and mesoporous material, we synthesized surface multi-functionalized magnetic mesoporous material, and applied it to selectively concentrate small molecules in environmental samples of complex matrix. The more details are as follows:In chapter1, it summarized the development of chromatography technique in environmental analysis and the pretreatment of complex samples. Firstly, it introduced all kinds of chromatographic separation and analysis methods which are applied to the environmental sample analysis in recent years, and then described the main technologies applied to the sample pretreatment according to the distinguishing features of complex system. Combined with the development of magnetic materials, it expounded the solid phase micro-extraction approaches based on functionalized magnetic micro-/nano-materials in environmental analysis. Finally, the purpose and significance of this dissertation were discussed.In chapter2, microwave-assisted extraction (MAE) followed by CE was developed for the fast analysis of catechin and epicatechin in green tea. In the proposed method, catechin and epicatechin in green tea samples and chlorogenic acid (CA) in tobacco residues were rapidly extracted by MAE technique, and then analyzed by CE. The MAE conditions and the method’s validation were studied. It is found that compared with conventional ultrasonic extraction (USE) and reflux extraction (RE), the extraction by MAE is very fast, and only lor4min is enough to completely extract catechin and epicatechin in green tea sample or chlorogenic acid (CA) in tobacco residues. The method validations were also studied in this work. The calibration curves all show good linearity for catechin, epicatechin and chlorogenic acid respectively. The RSD values for catechin, epicatechin and CA are0.65,2.58and4.28%respectively. The proposed method has good recoveries, which are118%for catechin,120%for epicatechin and89%for CA. The proposed method was successfully applied to determination of the catechin and epicatechin in different green tea samples and CA in tobacco residues. The experiment results have demonstrated that the MAE following CE is a simple, fast and reliable method.In chapter3, core-shell magnetic mesoporous microspheres with C18-functionalized interior pore-walls were synthesized through coating Fe3O4microspheres with a mesoporous inorganic-organic hybrid layer with a n-octadecyltriethoxysilane (C18TES) and tetraethyl orthosilicate (TEOS) as the silica source and cetyltrimethylammonia bromide (CTAB) as a template. The obtained C18-functionalized Fe3O4@mSiO2microspheres possess numerous C18groups anchored in the interior pore-walls, large surface area (274.7m/g, high magnetization (40.8emu/g) and superparamagnetism, uniform mesopores (4.1nm), which makes them ideal absorbents for simple, fast, and efficient extraction and enrichment of hydrophobic organic compounds in water samples. Several kinds of phthalates were used as the model hydrophobic organic compounds to systematically evaluate the performance of the C18-functionalized Fe3O4@mSiO2microspheres in extracting hydrophobic molecules by using a gas chromatography-mass spectrometry. Various parameters, including eluting solvent, the amounts of absorbents, extraction time and elution time were optimized. Hydrophobic extraction was performed in the interior pore of magnetic mesoporous microspheres, and the materials had the anti-interference ability to macromolecular proteins, which was also investigated in the work. Under the optimized conditions. C18-functionalized Fe3O4@mSiO2microspheres were successfully used to analyze the real water samples. The results indicated that this novel method was fast, convenient and efficient for the target compounds and could avoid being interfered by macromolecules.In chapter4, magnetic Fe3O4@mesoporous SiO2(Fe3O4@mSiO2) microshperes with phenyl group-functionalized interior pore-walls were synthesized through a facile one-pot co-condensation approach, and were successfully used as solid-phase extraction (SPE) sorbents to the extraction and enrichment of bisphenol A from human urine. The obtained phenyl group-functionalized Fe3O4@mSiO2microspheres possess abundant silanol groups in the exterior surface and numerous phenyl groups anchored in the interior pore-walls, as well as a large surface area (273.5m2/g), superparamagnetism and uniform mesopores (3.3nm), which make them promising SPE absorbents for efficient extraction and preconcentration of aromatic compounds from complex biological samples such as human urine. Bisphenol A was selected as the model aromatic compound to investigate the extraction ability of the as-made materials by using Liquid chromatography-Ultraviolet detector (LC-UV). Various parameters, including the eluting solvent, the amounts of absorbents and the extraction time, were optimized. In addition, the effect of pH value on the extraction was also investigated. The extraction was performed in the interior pores of the magnetic mesoporous microspheres by van der Waals and π-π interactions. Under the optimized conditions, phenyl group-functionalized Fe3O4@mSiO2microspheres were successfully used to analyze bisphenol A in the human urine samples. The results indicated that this proposed method based on phenyl group-functionalized Fe3O4@mSiO2microspheres was fast, convenient and efficient for extraction and analysis of the target compound of bisphenol A in biological samples.In summary, based on the latest sample pretreatment techniques, this theme developed microwave-assisted extraction and solid phase extraction based on magnetic materials. Especially solid phase extraction based on magnetic materials, which respectively makes use of hydrophobic and hydrophobic, van der Waals and π-π interaction and size exclusion effect, provided convenient and effective approaches for the extraction and enrichment of small pollutants in complex system. |
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