| Carbon nanotubes (CNTs) show greatly considerable application potential in the fields of materials, biosensors, catalyst carrier, biomedicine and seperation science for their unique carbon structures and outstanding physicochemical properties. CNTs, especially single-walled carbon nanotubes (SWNTs), are excellent materials for sample enrichment due to their large surface areas and strong adsorption ability. However. CNTs are macromolecules that are made up of thousands of carbon atoms in the delocalized conjugation system. CNTs can hardly be dissolved in almost any solvents and they are easy to bundle together, which hampers their potential applications. The solubility of CNTs can be improved by functionalization which could widely expand their applica-tions.Solid-phase microextraction (SPME), which integrates sampling, extraction, preconcentration, and sample introduction into a single step, is a novel sample pretreatment technique in the last decade. It has been successfully introduced to many fields such as environmental, food and bio-medical samples. However, most commercial available fibers are prepared by the method of physical absporption and show poor thermal durability and terminated lifespan, which limit their broader applications. The sensitivity of SPME teachnology can be greatly enchanced for the good absorption ability of fiber coating. Therefore, the key of SPME technique is the coating materials of fibers. It is of great importance to develop novel fiber coatings with high absorption ability, good sensitivity, thermal stability and long lifespan.In this paper, the structure of SWNTs was modified by carboxylation, chlorination and polymer functionalization. The modified SWNTs was used for the preparation of three kinds of SPME coating fibers with sol-gel method. The performances of the three coating fibers were evaluated by the analysis of organochlorine pesticides, chlorophenols, alkylphenols, chlorine organic carriers and polybrominated diphenyl ethers, etc. Their applications in actual samples were also performed by detecting various analytes in environmetal, food and industrial samples. The main contents are described as follows:1. Review. A brief overview of the structure types, physicochemical characteristics, preparation of CNTs is presented. This chapter mainly reviewed the applications of CNTs in separation science, which were included of stationary phase in gas chromatography and liquid chromatography, applications in electroanalytical chemistry, preconcentration materials for solid-phase extraction and SPME. Meanwhile, a brief introduction to Sol-gel technique was also reviewed.2. Preparation of functionalized single-walled carbon nanotubes and their sol-gel coated fibers. The modified SWNTs, which was prepared by the method of carboxylation, chlorination and polymer functionalization, was used for the preparation SPME coating fibers containing TSO/SWNTs, SWNTs-PEG, and SWNTs-TSO fibers with sol-gel method. The structures of the modified SWNTs were confirmed by infra-red and Raman spectrum. The morphological structure of the 3 kinds of fibers were investigated by scanning electron micrograph technique.3. Evaluation and application of TSO/SWNTs coating. Headspace (HS) SPME based on TSO/SWNTs coating was used to extract several chlorophenols (CPs) and organochlorine pesticides (OCPs) from aqueous samples prior to their determination by GC with electron capture detection. The main parameters affecting microextraction and the conditions of the thermal desorption in the GC injector were optimized:30 min of extraction at 50℃,3 min of desorption at 250℃.900 r/min of stirring rate and with the concentration of 0.9 g mL-1 of NaCl in aqueous samples. Compared with commercial SPME fibers, the fiber presented better selectivity and sensitivity. The repeatability expressed as relative standard deviation ranged from 4.1% to 8.2% and the fiber-to-fiber reproducibility for four prepared fibers was between 6.5% and 10.8%. Linear responsewas found for the concentration range between 2 and 1000 ng L-1(20-1000 ng L-1for CPs), and the limits of detection were in the range from 0.07 to 4.36 ng L'. Furthermore, the prepared fiber showed good accumulation ability towards alkylphenols and bisphenol A in purified water samples. The HS-SPME method had low detection limits, and good reproducibilities when coupled to GC-FID. Recovery was tested with spiked purified water samples, with values ranging from 89% to 94%.4. Evaluation and application of sol-gel SWNTs-PEG coating. Several parameters affecting headspace microextraction procedure were optimized by using SWNTs-PEG fiber for the analysis of eleven COCs in simulative sweat samples:30 min of extraction at 40℃,3 min of desorption at 300℃,0.36 g mL-1 of NaCl. Compared with the commercial PA, PDMS and PDMS/DVB fibers, the sol-gel SWNTs-PEG fiber showed higher extraction efficiency, better thermal stability and longer life span. The developed method had low limits of detection, wide linear range and good precision. The optimized HS-SPME method was successfully applied for the analysis of trace COCs in textiles, the recoveries of the analytes indicated that the prepared SWNTs-PEG fiber had wide application fields and good prospect.5. Evaluation and application of sol-gel SWNTs-TSO fiber. A group of parameters affecting extraction capacity of SWNTs-TSO coating were optimized by analyzing 7 polybrominated diphenyl ethers. Under optimized conditions, the limits of detection were in the range from 0.08 to 0.8 ng L-1, linear responsewas found for the concentration range between 5 and 500 ng L-1, the repeatability expressed as relative standard deviation ranged from 2.3% to 7.4%. The novel coated fiber showed higher extraction efficiency compared with the commercial SPME fibers. The developed method had low limits of detection, wide linear range and good precision. Sol-gel SWNTs-TSO fiber, coupled to HS-SPME-GC-ECD method, was finally applied for the determination of polybrominated diphenyl ethers in reservoir water and wastewater samples. |
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