Fabrication Of Composite Metal Oxide Coatings On Nickel-titanium Alloy Fiber And Their Applications In Solid-phase Microextraction

Solid phase microextraction（SPME）which integrates sampling,extraction,concentration and injection into a single step,is an easy to operate,convenient and environmental-friendly pretreatment technology.Since the commercial available fused-silica fibers have some shortcomings such as easy to break during usage and swelling in organic solvents.In this thesis,novel nickel-titanium oxide nanostructures were developed on the surface of the nickel-titanium alloy（NiTi）wire and further used for the enrichment and extraction of target analytes in real water samples.In Chapter 1,the basic principle,extraction devices,extraction modes,the fiber coating preparation,applications and the influence factors of SPME technology were summarized.In addition,persistent pollutants PAHs in the environment were briefly introduced.In Chapter 2,a bimetallic NiTi oxide nanocomposites（NiTi ONCs）coating was in situ grown on the original NiTi fiber substrate by direct anodization at low voltage.The morphology and elemental composition of different NiTi fibers were characterized by scanning electron microscopy（SEM）and energy dispersive X-ray spectroscopy（EDX）.The anodization parameters including electrolyte composition,time,voltage and temperature were investigated and optimized.Under the optimized conditions,the NiTi ONCs coating was prepared with uniform morphology and large specific surface area.Four types of representative aromatic compounds were used as model analytes to evaluate the adsorption performance of the NiTi@NiTi ONCs fiber.Compared with PDMS and PA fibers,the NiTi@NiTi ONCs fiber has higher selectivity and extraction efficiency for PAHs.The extraction parameters for SPME were further optimized.Under the optimized conditions,the analytical performance of the NiTi@NiTi ONCs fiber for PAHs was investigated.Good linearity was obtained in the concentration ranges of 0.05μg·L^-1-200μg·L^-1 with correlation coefficients above 0.999.LODs are in the range of 0.013μg·L^-1-0.145μg·L^-1（S/N=3）.RSDs of the single fiber ranged from4.0%to 5.3%and from 4.7%to 6.3%for intra-day and inter-day analyses of PAHs at the spiking level of 50μg·L^-1,respectively.RSDs for the fiber-to-fiber reproducibility varied from 5.9%to 7.0%for five fibers fabricated in different batches.Finally,the NiTi@NiTi ONCs fiber was applied to the determination of PAHs in five water samples and the relative recoveries ranged from 84.4%to 109%were achieved.In Chapter 3,a novel nickel-titanium bimetallic oxide composites nanorods（NiTi ONRs）coating was grown on the surface of NiTi fiber by high voltage anodization.The morphology and elemental composition of different NiTi fibers were characterized by SEM and EDX.The anodization parameters including electrolyte composition,time and temperature were optimized.Four types of representative aromatic compounds were used as model analytes to evaluate the adsorption performance of the NiTi@NiTi ONRs fiber.The extraction result showed that the NiTi@NiTi ONRs fiber exhibited better selectivity for PAHs.Under optimized conditions(salt concentration,20%;p H,7.0;extraction temperature,45 ^oC;stirring rate,600 r·min^-1;extraction time,45 min;desorption time,2 min),the correlation coefficients were above 0.999.The recoveries ranged from 95.3%to 103%.The LODs were in the range of 0.014μg·L^-1-0.136μg·L^-1.The intra-day and inter-day RSDs of a single fiber were in the range of 4.0%-5.4%and5.0%-6.7%,respectively.In Chapter 4,the newly prepared fiber was obtained by annealing the NiTi@NiTi ONRs fiber.Four types of representative aromatic compounds were used as model analytes to evaluate the adsorption performance of the NiTi@NiTi ONRs annealing at 600 ^oC（NiTi@NiTi ONCs（600））fiber.The extraction result showed that the NiTi@NiTi ONCs（600）fiber exhibited better selectivity for PAHs.Under optimized conditions(salt concentration,25%;p H,7.0;extraction temperature,50 ^oC;stirring rate,600 r·min^-1;extraction time,50 min;desorption time,2 min),good linearity was obtained in the concentration ranges of 0.05μg·L^-1-200μg·L^-1 with correlation coefficients above 0.999.The LODs were in the range of 0.014μg·L^-1-0.144μg·L^-1.RSDs for the fiber-to-fiber reproducibility varied from 6.5%to 8.2%for five fibers fabricated in different batches.In addition,the home-made SPME fibers in this thesis had stable adsorption efficiency after 210 extraction and desorption operations,the fiber preparation process was precisely controllable,and the cost was low.