Fabrications And Applications Of In Situ Growth Of Oxide Coatings On NiTi Based Solid-phase Micro-extraction Fiber

Solid-phase micro-extraction(SPME)is a kind of highly efficient sample pretreatment technology.Compared with fused silica substrate,the metal substrate has attracted great interests due to its advantages of good rigidity,high thermal stability and rapid simple preparation method.In this thesis,the fabrication of three kinds of oxides coated nickel-titanium alloy solid-phase micro-extraction fiber was studied and their applications in environmental water samples were evaluated at the same time.This thesis was divided into the following sections:Chapter 1:The extraction mechanism,the advantages and disadvantages of SPME,the application fields,the different coating materials of SPME fiber and the choices of coatings as the core part of SPME were introduced.Then the significance of the subject and research interests were presented.Chapter 2: By the acid treatment method,the composite oxides coating with high surface area were prepared on the Ni Ti alloy wire.The fiber has good extraction efficiency and selectivity for UV filters,by using HPLC with Ultraviolet(UV)detector.Under the optimized conditions,the calibration curves were linear in the range of 0.1-300?g·L-1 for target UV filters with LODs of 0.025-0.097?g·L-1.The intra-day and inter-day precision of the proposed method with the single fiber were4.9-5.8% and 5.5-6.4%,respectively,and the fiber-to-fiber precision ranged from6.3% to 7.1% for different batches.The preparation of the fiber is fast and simple.The prepared fiber has high stability and good reproducibility.Besides,the developed method has been successfully applied to the determination of UV filters in environmental water samples.Chapter 3: An oriented oxide nanotubes coating was in situ grown on a Ni Ti alloy wire by direct electrochemical anodization for the first time.The morphology and the composition of the resulting coating showed that the surface of the anodized Ni Ti alloy wire was uniform,rich in titania and had a high surface area.The coating exhibited high extraction capability,good selectivity and rapid mass transfer for weakly polar UV filters coupled to HPLC-UV.Under the optimized conditions,thecalibration curves were linear in the range of 0.1-300?g·L-1 for target UV filters with LODs of 0.019-0.082?g·L-1.The intra-day and inter-day precision of the proposed method with the single fiber were 5.3-7.2% and 5.9-7.9%,respectively,and the fiber-to-fiber reproducibility ranged from 6.3% to 8.9% for different batches.Finally,its applicability was evaluated by the extraction and determination of target UV filters in environmental water samples.Chapter 4: The surface of the anodized Ni Ti alloy wire was modified via thermal treatment,and the needle-like Ti O2 coating was obtained.The morphology and the composition of the resulting coating showed that the surface of the anodized Ni Ti alloy wire was compact and had a high surface area.When coupled with HPLC-UV detector,the calibration curves were linear in the range of 0.1-300 ?g·L-1 for target UV filters with LODs of 0.028-0.073?g·L-1 under the optimized conditions.The intra-day and inter-day precision of the proposed method with the single fiber were6.0-7.5% and 6.8-8.3%,respectively.Finally,its applicability was evaluated by the extraction and determination of target UV filters in environmental water samples.