In Situ Fabrication Of TiO₂ Nanostructured Solid-phase Microextraction Fibers And Their Applications

In the past ten years, great efforts were devoted continuously to synthesis of different dimensional TiO₂ such as nanoparticles, nanotubes, nanowires and nanosheets by a variety of technologies, due to its excellent thermal and chemical stability, low cost, good biocompatibility, high corrosion-resistance and non-toxicity. In this thesis, in-situ anodization was used to successfully prepare TiO₂ nanosheets?TiO₂NS? coating on Tisubstrate in ethylene glycol with concentrated NH4 F, following by self-assembly or annealing to modify the surface of TiO₂NS-Tifiber. The fabricated TiO₂NS-Tifiber were used to enrich and test trace amount of pollutants in real environmental water samples coupled to high performance liquid chromatography-UV detection?HPLC-UV?. This thesis mainly consists of four chapters:Chapter 1: Current advances in solid-phase microextraction?SPME? fibers with metal wires as supporting substrates and recent development of related techniques were briefly introduced such as sol-gel technology, electrochemical procedures and in-tube SPME. The mechanism of SPME and the nature of target analytes were reviewed in detail. Finally, the application of this proposed method was discussed.Chapter 2: Both electrochemical anodization and self-assembly were used to fabricate TiO₂ nanosheets, followed by high density of hydroxyl groups were decorated on the surface of TiO₂NS-Tiwire via silylation reaction.SPME-HPLC method was used to concentrate, detect and quantify naphthalene?Nap?, phenanthrene?Phe?, fluoranthene?Flu? and benzo[a]pyrene?B[a]p? in different sections of Yellow River and other water samples. In the optimal conditions, good linearity was obtained for target analytes in range of 0.5-300 ?g·L-1 with correlation coefficients?R2? ?0.9991, relative standard deviation was less than 9.45%, the limits of detection?LODs? for all analytes based on signal-to-noise of 3 was between 0.008-0.043 ?g·L^-1. Results indicated that compared with two kinds of commercial available SPME fibers, phenyl-functionalized TiO₂NS?ph-TiO₂NS? coating fiber exhibited high extraction efficiency and good selectivity for PAHs and could be used for more than 250 extraction and desorption cycles without the loss of extraction capability.Chapter 3: After Tiwire was anodized and dried, the TiO₂NS-Tifiber was annealed in tubular furnace under N₂. TiO₂ nanoparticles generated on the surface of TiO₂ nanosheets via condensation reaction between two adjacent hydroxyl groups after anodization. The influence of extraction time, desorption time, extraction temperature, pH and salting-out effect on the extraction performance were studied and optimized in detail. Under the optimal conditions, SPME-HPLC method was used to investigate the distribution and pullution of benzophenone-3?BP-3?, ethylhexyl dimethyl p-aminobenzoate?OD-PABA?, ethylhexyl methoxycinnamate?EHMC? and ethylhexyl salicylate?EHS? in different sections of Yellow River and other water samples. Results indicated that the Yellow River water in Lanzhou Section has been slightly polluted by UV filters. From west to east, the concentration of UV filters in downstream water was higher than that in upstream water.Chapter 4: Electrochemical method was employed to fabricate TiO₂ nanosheets, followed by annealing in tubular furnace under N₂. SPME-HPLC method was used to concentrate, detect and quantify naphthalene?Nap?, phenanthrene?Phe?, fluoranthene?Flu? and benzo[a]pyrene?B[a]p? from different sections of Yellow River and other water samples. In the optimal conditions, good linearity was obtained for target analytes in range of 0.05-300 ?g·L-1 with correlation coefficients?R²? ?0.9991, relative standard deviation was less than 10.5 %, and LODs for all analytes based on signal-to-noise of 3 was between 0.019-0.367 ?g·L^-1. The proposed method was successfully applied to the extraction and quantitation of PAHs in the real environment water samples.