| Solid phase microextraction?SPME?preprocessing technology is simple to operate,low-cost,and the waste liquid in the operation process can be effectively recovered and processed.This technology is based on the solid phase extraction?SPE?as a prototype and developed,and as well as improved some disadvantages of SPE,such as low recovery and easy clogging of adsorbent pores.SPME has been widely used in the analysis of water,air,soil and other environmental samples.In this paper,the nickel-titanium alloy?NiTi?was modified,and the different morphologies of zinc-aluminum layered double hydroxide?ZnAl-LDH?coatings were assembled on the surface.Meanwhile,the enrichment performance of ultraviolet filters?UVFs?was evaluated.The thesis consists of the following chapters:In Chapter 1,the basic principles,experimental devices,and coating classification,and as well as preparation methods of SPME coatings are briefly introduced.Then,the influencing factors and application prospects of SPME technology are introduced reviewed.In addition,UVFs are also described.At last,the idea and main content of this research are presented.In Chapter 2,a new flower-like ZnAl-LDH coating was firmly fabricated on a superelastic NiTi wire.Herein,the NiTi wire was hydrothermally treated for the in-situ growth of nickel and titanium oxide nanoflakes?NiTiONFs?and used as a fiber support for subsequent growth of ZnAl-LDH nanoflowers.The resulting coating was able to selectively extract the studied ultraviolet filters?UVFs?more effectively and quickly in comparison with the commercial polyacrylate and polydimethylsiloxane fibers.This fiber shows long recycling lifetime due to the ZnAl-LDH coating embedded into the active NiTiONFs support with high mechanical stability.For this purpose,main experimental parameters including temperature,stirring rate,extraction and desorption time,and ionic strength were investigated and optimized in detail.Under the optimized conditions,good linearity was obtained for the developed SPME-HPLC-UV method with the NiTi@NiTiONFs@ZnAl-LDH fiber.Limits of detection were between 0.009?g L-1 and 0.052?g L-1 for five UVFs.Intra-day and inter-day relative standard deviations?RSDs?for single fiber repeatability were less than 6.4%and 6.6%for five replicate extractions of UVFs at the spiking level of 50?g L-1.The developed method was successfully used for the determination of UVFs in snow water,river water and wastewater samples.The relative recoveries of 77.2%-109%were achieved.Thus the developed method could be potentially applied to selective enrichment and determination of UVFs in different environmental water samples.After 120 extraction and desorption cycles,the recovery of 83.6%-101%was obtained for five replicative analyses.Moreover,the fiber preparation is precisely controllable.In Chapter 3,a hydrothermal method was used for the formation of ZnAl layered double hydroxide nanoflakes?ZnAl-LDHNFs?on NiTiONFs fabricated on NiTi fibers.Characterizations using scanning electron microscopy?SEM?and energy dispersive X-ray spectroscopy?EDX?showed that the coating presents a cross-hexagonal nanosheet morphology with a thickness of about 200 nm by changing the hydrothermal temperature and reaction time.Under the optimal conditions(extraction temperature,35?;stirring rate,400 r·min-1;extraction time,40 min;desorption time,4 min;NaCl,3%),LODs ranged from 0.009?g·L-1-0.051?g·L-1 for five UVFs.RSDs were less than 6.3%and 7.1%for intra-day and inter-day analyses of UVFs at the spiking level of50?g·L-1 with the single fiber?n=5?,respectively.The recoveries of five UVFs in real water samples ranged from 71%-101%.Furthermore,the fabricated fiber has good recycling stability.After 200 extraction and desorption cycles,the satisfactory recovery was obtained without significant loss.Moreover,the fiber preparation is precisely controllable.In Chapter 4,Zn-Al oxide nanoflakes?ZnAlONFs?was studied as a potential adsorbent.ZnAl-LDHNFs based on NiTiONFs were prepared on the NiTi fiber substrates by the hydrothermal method,and calcined at 400?for 4 h.The adsorption results show that the adsorption capacity of ZnAlONFs coating calcined at 400?for UVFs is better than the former ZnAl-LDHNFs.Under optimized conditions(extraction temperature,35?;stirring rate,400 r·min-1;extraction time,30 min;desorption time,4 min;NaCl,3%),the correlation coefficients?r?obtained by the SPME-HPLC-UV method developed using NiTi@NiTiONFs@ZnAlONFs?400?fiber were greater than0.999.In addition,LODs ranged from 0.007?g·L-1-0.021?g·L-1 for five UVFs.RSDs were less than 6.0%and 7.3%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 recoveries of five UVFs in real water samples ranged from 79.8%-102%.Furthermore,the fabricated fiber has good recycling stability.After 170 extraction and desorption cycles,the satisfactory recovery was obtained without significant loss.Moreover,the fiber preparation is precisely controllable. |
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