Fabrication Of Titanium-based Oxide Solid-phase Microextraction Fibers And Their Applications In The Analysis Of Environmental Water

Solid-phase microextraction?SPME?is a novel solvent-free sample preparation technique.Compared with fused-silica fibers with a polymeric coatings,the metal-based fiber has high mechanical strength with quick and simple coating preparation methods.Therefore,it has attracted great interest and attention from many researchers.In this thesis,the fabrication of three different titanium?Ti?SPME fibers was studied,and their applicationsin,the enrichment,separation and determination of different pollutants in environmental water samples were also evaluated.This thesis consists of four chapters:Chapter 1: The basic principles,devices,extraction steps and preparation methods of SPME coatings are briefly introduced.Then,the influential factors,combined technology and applications of SPME are reviewed.Polycyclic aromatic hydrocarbons?PAHs?and UV filters?UVFs?are also described.Finally,the ideas and main contents of this thesis are introduced.Chapter 2: TiO₂ has superior thermal and chemical stability,nanostructure-forming ability and good adsorption capacity.Titania nanowires?TiO₂NWs?were in-situ grown on the titanium?Ti?wire by hydrothermal process in alkali so lution.Thereafter,the TiO₂ NWs coated Ti?Ti@TiO₂NWs?fiber was annealed at 800 oC,and the rock-like TiO₂ coating?Ti@TiO₂NRs?was fabricated on the Ti fiber substrate.Coupled to high-performance liquid chromatography with ultraviolet detection?HPLC-UV?,the SPME performance of the rock-like TiO₂ coating was comparatively studied using typical aromatic compounds as model analytes.As compared with the commercial polydimethylsiloxane?PDMS?fiber,the rock-like TiO₂ coated Ti fiber showed high extraction capability and good extraction selectivity for.Under the optimized conditions,the developed method presented linear ranges from 0.05 ?g·L-1 to 400 ?g·L-1 with correlation coefficients higher than 0.999 and limits of detection?LODs?from 0.013 ?g·L-1 to 0.065 ?g·L-1.Relative standard deviations?RSDs?were below 5.4% and 6.2% for intra-day and inter-day analyses of PAHs at the spiking level of 50 ?g·L-1 with the single fiber?n = 5?,respectively.The developed method was successfully applied to the selective enrichment and determination of target UVFs in environmental water samples with recoveries from 83.8% to 109% and RSDs from 4.8% to 9.1%.Moreover,the fabrication of the rock-like TiO₂ coated Ti fiber is precisely controllable and stable for at least 300 extraction and desorption cycles.Chapter 3: This part describes a facile fabrication of silica nanosheets?Si O2NSs?on a Ti fiber substrate via hydrothermal reaction hyphenated with electrophoretic deposition?EPD?.Surface morphology and elemental composition revealed the in-situ growth of titania nanowires on the Ti wire?Ti@ TiO₂NWs?by hydrothermal process in alkali solution and subsequent EPD of the homogeneous Si O2 coatings on the Ti@TiO₂ NWs fiber with large surface area.After annealing at 550 oC,the fabrication of homogeneous Si O2 NSs coating on the Ti@ TiO₂NWs?Ti@TiO₂NWs@Si O2NSs?fiber was achieved.The SPME performance of the Si O2 coatings before and after annealing was comparatively studied using typical aromatic compounds as model analytes for the first time coupled to HPLC-UV.The results demonstrated that the Ti@TiO₂NWs@Si O2 NSs fiber has excellent extraction selectivity and capacity for UVFs compared to a commercial polyacrylate?PA?fiber.Under the optimized conditions,the developed method with the Ti@TiO₂NWs@Si O2 NSs fiber presented linear ranges from 0.02 ?g·L-1 to 400 ?g·L-1 with correlation coefficients higher than 0.999 and LODs from 0.004 ?g·L-1 to 0.059 ?g·L-1.RSDs were below 5.3% and 6.2% for intra-day and inter-day analyses of UVFs with the single fiber,respectively.The developed method was succes sfully applied to the selective enrichment and sensitive determination of target UVFs in real water samples with recoveries from 83.6% to 104%.Moreover,this fiber has controllable preparation reproducibility and is stable for at least 200 extraction and desorption cycles.Chapter 4: Titania nanorods?TiO₂NRs?were in-situ grown on the Ti wire by electrochemical anodization.Thereafter,the Ti@ TiO₂ NRs fiber was annealed at 800 oC and the nanoparticle-like TiO₂ NRs coating was fabricated on the Ti fiber subs trate.Coupled to HPLC-UV,the SPME performance of the annealed Ti@TiO₂ NRs fiber was comparatively studied using typical aromatic compounds as model analytes.As compared with the commercial PA fiber,the annealed Ti@TiO₂ NRs fiber showed high extraction capability and good extraction selectivity for UVFs.Under the optimized conditions,the proposed method presented linear ranges from 0.05 ?g·L-1 to 300 ?g·L-1 with correlation coefficients above 0.999 and LODs range from 0.005 ?g·L-1 to 0.045 ?g·L-1.RSDs were below 5.4% and 6.4% for intra-day and inter-day analyses of UVFs at the spiking level of 50 ?g·L-1 with the single fiber?n = 5?,respectively.The proposed method was successfully applied to the selective enrichment and sensitive determination of target UVFs in environmental water samples with recoveries from 85.0% to 113% and RSDs from 4.2% to 7.8%.Moreover,the fabrication of the annealed Ti@TiO₂ NRs fiber is precisely controllable and stable for at least 200 extraction and desorption cycles.