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Research of Solid-phase Extraction Based on Graphene Composite and Its Application in High-performance Liquid Chromatography Analysis

Author: LiJing
Tutor: HuangKeJing
School: Xinyang Normal University
Course: Analytical Chemistry
Keywords: solid phase extraction high-performance liquid chromatography graphene functionalization
CLC: O658.2
Type: Master's thesis
Year: 2013
Downloads: 37
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Abstract


With the development of industrial production, pollution problems in the environment is getting more and more serious, as a result, the measurement of pollutants in the environment, has always been an important research direction in the field of environmental science. Until now, some analytical methods were employed in the detection of both inorganic and organic pollutants residue in the environment, such as gas chromatography, high performance liquid chromatography, capillary electrophoresis, atomic absorption spectrometry and atomic emission spectrometry, et al. Due to the low concentrations of pollutants residue in environment samples, general analytical instrument can’t direct detection it, and higher matrix interferences of some complex sample, sample pretreatment processes have to be employed to for the preliminary enrichment and purification of target materials in sample.Traditional sample pretreatment technologies can’t reach the requirement of environmental analysis on account of the complicated time-consuming operation、 difficult to automation、high dosage of organic solvent which are easy to cause secondary pollution to environment, and insufficient accuracy and precision, Therefore, development of simple、rapid and efficient sample pretreatment technology, has always been one of the important research direction in environmental science. So far many new sample pretreatment technologies have been developed, such as solid phase extraction、 solid phase micro-extraction、liquid phase extraction、liquid phase micro-extraction and supercritical fluid extraction、ultrasonic assisted extraction, matrix solid-phase dispersion, et al. Among them, solid phase extraction are widely used in a variety of sample substrate pretreatment owing to the high enrichment efficiency、easy automation and low dosage of organic solvent.In the solid phase extraction, the choice of the adsorbent is suitable decided the extraction enrichment efficiency of high and low, at the same time, influence the extraction is successful or not. Commercial solid phase extraction adsorbents including C8、C18、silica gel, et al. But these materials can’t reach some analysis work requirements in the selective adsorption and enrichment efficiency, therefore, represented by carbon nanotubes of carbon nanomaterials, with its unique structure and properties has attracted widespread attention, gradually replaced the conventional adsorption materials. For example, some research results have shown that graphene has unique two-dimensional nano structure, specific surface area is large, and is a kind of good adsorption material. In view of this, this article choose graphene as the research object, and investigate the application potential of the modification and functionalization of graphene composites as solid phase extraction sorbents. This thesis is mainly composed of four chapters:The first chapter:The development of sample preparation technology in recent years were reviewed in this chapter, and introduces the new types of solid phase extraction sorbents such as carbon nanotubes、graphene、molecularly imprinted polymer magnetic nanoparticles and biological adsorbent in detail, The future development in the use of these materials were also simply demonstrated.The second chapter:Graphene functionalized with (3-Aminopropyl) triethoxysilane (APTES)(GR-A) was synthesized in this chapter, and this material was characterized by Fourier transform infrared spectroscopy (FT-IR)、scanning electron microscope (SEM). It was used as a novel solid-phase extraction (SPE) adsorbent. An analytical method based on SPE combined with high-performance liquid chromatography (HPLC) was established for the determination of polycyclic aromatic hydrocarbons (PAHs) in environmental waters. Several condition parameters were optimized to achieve good sensitivity and precision, such as the analytes were eluted by0.3mL acetonitrile, Scope of the pH was6-7, and sample volume was100mL. The experimental results indicated that there were excellent linear relationships between peak area and the concentration of PAHs over the range of1-100μg/L, and the precisions (RSD) were1.7-2.9%under the optimal conditions. The detection limits were0.029-0.1μg/L (S/N=3). The recoveries of PAHs spiked in environmental water samples ranged from84.6to109.5%, it indicated that the method is suitable for the detection of trace concentrations of PAHs in environmental system. All the results shows that GR-A was synthesized in this chapter was an excellent solid phase extraction adsorbents which has application value.The third chapter:In this work, graphene modified silica gel (GR-SiO2) sorbents were prepared and it was characterized by FT-IR、SEM and X-ray to assure the successful bonding of GR on the surface of silica gel. Then an analytical method based on SPE combined with HPLC-UV was established, and the GR-SiO2sorbents were served as SPE sorbents for the enrichment of PAHs in environmental water samples and sulfonamides (SAs) in milk. For all PAHs analytes:several condition parameters, such as eluent type (acetonitrile), eluent volume (0.2mL), sample volume (75mL) and methanol content (15%) were optimized to achieve good sensitivity and precision for the analytes. Under the optimized conditions, for all PAHs analytes, the GR-SiO2sorbents showed good linearities with R (>0.9933), low detection limits (0.012-0.082ng/L), and wide linearity (0.01-600μg/L). The repeatability of the intraday and interday RSDs were below5.2%and8.2%, respectively. The method was applied to simultaneous analysis of six PAHs with satisfactory recoveries of84.7-114.0%. For all SAs analytes, it indicated that the highest enrichment efficiency was obtained for five SAs when0.1mL acidic methanol was selected as eluent, the pH, volume of water sample were pH5,75mL respectively, the specific volume of acidic and methanol was1:1.5. The GR-SiO2sorbents showed low detection limits (0.027-0.078μg/L), and wide linearity (0.1-100μg/L). The repeatability of the intraday and interday RSDs were below6.9%and10.3%, respectively. The method was applied to simultaneous determination of five SAs in milk with recoveries of88.3-113.6%. It indicated that the method is suitable for the detection of trace concentrations of PAHs and SAs in environmental system. All the results shows that GR-SiO2was synthesized in this chapter was an excellent solid phase extraction adsorbents which has application value, and is expected to commercialization of the production.

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CLC: > Mathematical sciences and chemical > Chemistry > Analytical Chemistry > Separation of elements and compounds > Extraction method
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