Fabrication Of Silicon-based Nanostructured Fibers On The Nickel-titanium Substrates And Their Applications In Solid-phase Microextraction

Solid-phase microextraction（SPME）is an efficient and solvent-free sample preparation technology.Compared with fused silica substrate,the metal substrate has attracted great interests due to its advantages of good mechanical strength,high thermal stability and rapid simple preparation method.In this thesis,the fabrication of three kinds nickel-titanium alloy（NiTi）SPME fibers was studied and their applications in environmental water samples were evaluated.The thesis consists of the following chapters:In Chapter 1,an introduction to SPME technique is described,including its theory,preparation of extraction coating,extraction modes,conditions optimization,application fields and their advances.In addition,ultraviolet filters（UV filters）and polycyclic aromatic hydrocarbons（PAHs）are briefly introduced.Then,the idea and main content of this research were presented.In Chapter 2,a new strategy for the immobilization of phenyl-functionalized silica nanoparticles（SiO₂NPs）onto the NiTi wires was presented.The homogeneous and compact SiO₂ NPs coating was achieved on the hydrothermally treated NiTi wires with large surface area by electrophoretic deposition（EDP）,and followed by self-assembled modification of phenyltrichlorosilane（PTCS）.Coupled to HPLC with UV detection,the extraction performance of the fabricated fiber was evaluated using typical aromatic compounds in direct-immersion mode of SPME.Due to its high extraction efficiency and good selectivity for UV filters,the novel fiber was employed to investigate the key factors affecting the extraction of UV filters.Under the optimized conditions,four UV filters presented good linearity with correlation coefficients（r）greater than 0.999,and limits of detection（LODs）ranged from 0.005 to 0.058 mg·L-1.The intra-day and inter-day relative standard deviations（RSDs）were from 3.9% to 4.8% and 4.5% to 5.6% for UV filters at the spiking level of 50 mg·L-1 with the single fiber,respectively.The relative recoveries of UV filters in spiked real water samples ranged from 80.6% to 110%.Moreover,the Ni O/Ti O2CNSs@SiO₂NPs-Ph fiber has high stability and good preparation reproducibility.The method is suitable for the selective concentration and sensitive detection of target UV filters from environmental water samples.In Chapter 3,SiO₂ nanosheets（SiO₂NSs）coating was successfully prepared on the NiTi wire after hydrothermal treatment by sol-gel method.The proposed method is simple and free of adhesive.The fabricated SiO₂ NSs are uniform and firmly adhered to the fiber substrate with good organic solvent resistance,high mechanical strength and long service life.The fiber exhibited some extraction selectivity for PAHs in water samples.Therefore,PAHs was used as model analytes to investigate the extraction performance of the SiO₂ NSs coating.The influences of stirring rate,extraction temperature,extraction time and ionic strength on the extraction efficiency were optimized coupled to HPLC with UV detection.Under the optimized conditions,five PAHs presented good linearity with correlation coefficients（r）greater than 0.999,and LODs ranged from 0.029 to 0.15 mg·L-1.The intra-day and inter-day RSDs were from 4.0% to 5.2% and 4.4% to 6.0% for PAHs at the spiking level of 50 mg·L-1 with the single fiber,respectively.The relative recoveries of five PAHs in real water samples ranged from 88.0% to 108%.Moreover,the Ni O/Ti O2@SiO₂ NSs fiber has good preparation reproducibility.The developed method is suitable for the concentration and the determination of target PAHs in environmental water samples.In Chapter 4,a novel silica-based SPME fiber was successfully fabricated by the immobilization of SiO₂ NSs onto the hydrothermally treated NiTi wire using sol-gel method,followed by self-assembled surface modification of PTCS.The extraction performance of the fabricated fiber was evaluated using typical aromatic compounds in direct-immersion mode of SPME.The fiber exhibits high extraction capability and good extraction selectivity for PAHs in water samples.The influences of p H,stirring rate,extraction temperature,extraction time,desorption time and ionic strength on the extraction efficiencies were optimized coupled to HPLC with UV detection.Under the optimized conditions,five PAHs presented good linearity with correlation coefficients（r）greater than 0.999,and LODs ranged from 0.013 to 0.11 m g·L-1.The intra-day and inter-day RSDs were from 4.1% to 5.9% and 4.8% to 6.8% for PAHs at the spiking level of 50 mg·L-1 with the single fiber,respectively.The relative recoveries of the five PAHs inreal water samples spiked at 10 mg·L-1 and 30 mg·L-1 ranged from 90.8% to 106% and93.6% to 103%,respectively.Moreover,the Ni O/Ti O2@SiO₂NSs-Ph fiber has high stability and good preparation reproducibility.The developed method is suitable for the concentration and the determination of target PAHs in environmental water samples.