Study On Fabrication Of Nanocomposite Coatings On NiTi Alloy Fibers And Their Applications In Solid-phase Microextraction

Solid phase microextraction(SPME)is a new green sample pretreatment technology.The fiber substrate is one of the key components of the SPME fiber,and its mechanical strength determines the durability of the fiber to a great extent.Compared with the commercially available SPME fibers based on fused silica,the SPME fibers based on Ni Ti fibers have superelasticity,high mechanical strength and good thermal stability.The coating preparation methods have attracted the interest of many researchers.In this thesis,the fabrication of three different oxides coated Ni Ti SPME fibers was explored,and their applications in the enrichment,separation and determination of polycyclic aromatic hydrocarbons(PAHs)in environmental water samples were evaluated.This thesis includes the following parts:Chapter 1: The principle,devices and extraction modes of SPME,the preparation methods of SPME coatings and the perspectives of its applications are briefly reviewed.Then the significance and research interest of this thesis are presented.Chapter 2: Phenyl modified mesoporous silica(MPS)particles were fabricated on the nickel-titanium(Ni Ti)wire as a SPME fiber by electrophoretic deposition and electrochemical anodization.Extraction performance of the fabricated Ni Ti fiber was evaluated coupled with high-performance liquid chromatography(HPLC).The linear ranges were between 0.02-500 μg·L-1 with their correlation coefficients(r)more than 0.9990.Limits of detection(LODs)were between 3.6 ng·L-1-5.2 ng·L-1.The intra-day and inter-day precision of the proposed method with the single fiber were 4.3%-5.1% and 4.9%-5.4%,respectively,and the fiber-to-fiber precision ranged from 6.0% to 6.9% for five fibers fabricated in different batches.In addition,the fiber is extracted and desorpted at least 200 times in SPME,and is fabricated in precisely controllable manner.The developed method has been successfully used for the enrichment and determination of PAHs in water,rainwater and domestic sewage,and the relative recovery is between 89.4% and 102%.Chapter 3: In situ growth of Ni-doped titania nanoflakes(Ti O2/Ni ONFs)with high specific surface area was performed on a Ni Ti wire in ethylene glycol solution(60%(v/v)H2O)containing 2.5%(w/v)Na OH by anodization for SPME.Extraction performance of the fabricated Ni Ti fiber was evaluated using PAHs as model analytes coupled with HPLC.The main parameters affecting SPME were optimized.Under the optimized conditions,the calibration graphs were linear in the range of 0.05~400 μg·L-1.The LODs of the proposed method were 0.011-0.058 μg·L-1.The intra-day and inter-day RSDs for the single fiber were4.3-6.0% and 4.7-6.9%(n=5),respectively.RSDs for fiber-to-fiber reproducibility ranged from 5.2% to 8.5%(n=5).The proposed method was successfully applied to the selective preconcentration and sensitive determination of target PAHs in river water and wastewater samples with relative recoveries from 89.2% to 102%.Chapter 4: Porous nanostructured coating was successfully in situ fabricated on the surface of a Ni Ti wire by anodization.The extraction performance of PAHs was studied under the optimized conditions and combined with HPLC-UV.The linear ranges of the analyte concentration were 0.05-400 μg·L-1 with r ≥ 0.999,The RSDs are less than 9.0%,The LODs are 0.009-0.122 μg·L-1.In addition,the Ni Ti fiber fabricated by this method has good extraction selectivity for PAHs.In situ assembly of nanoporous Ni O/Ti O2 coating on Ni Ti alloy wire is expected to play a greater role in SPME in the future.