Preparation Of Nanostructured Zinc Oxide Coating For Solid Phase Microextraction Fibers And Analytical Applications

Nowadays, commercial SPME coatings exist some drawbacks include fragility of fiber support, thermal instability and nonresistance organic solvents, fewer species,high cost and short life time, restrict its further application. In this paper, a convenient electrochemical deposition will be used for rapid preparation of nanostructured Zn O as fiber coatings for the enrichment and separation of ultraviolet and polycyclic aromatic hydrocarbons absorbing agents in environmental water samples followed by high performance liquid chromatography(HPLC) analysis.This thesis consists of four chapters:Chapter 1: Solid-phase microextraction(SPME) has been extensively used as a powerful sample preparation technique in analysis of trace organic analytes since its introduction by Pawliszyn and co-workers in the early 1990 s. As compared with traditional liquid-liquid extraction and solid-phase extraction, SPME is a simple,time-saving, sensitive and solvent-free technique by integrating sampling, extraction,concentration with sample introduction procedures for gas chromatography and high performance liquid chromatography(HPLC) in a single step. Therefore, the development of fiber coatings with excellent physicochemical properties has attracted considerable research attention in the past two decades. The latest reports are on the use of synthesized nanomaterials as extraction coatings in the fabrication of SPME fibers.Chapter 2: A novel zinc-zinc oxide(Zn-Zn O) nanosheets coating was directly fabricated on an etched stainless steel wire substrate as solid-phase microextraction(SPME) fiber via previous electrodeposition of robust Zn coating. The scanning electron micrograph of the Zn-Zn O nanosheets coated fiber exhibits a flower-like nanostructure with high surface area. The SPME performance of as-fabricated fiber was investigated for the concentration and determination of polycyclic aromatic hydrocarbons, phthalates and ultraviolet(UV) filters coupled to high performance liquid chromatography with UV detection(HPLC-UV). It was found that the Zn-Zn O nanosheets coating exhibited high extraction capability, good selectivity and rapid mass transfer for some UV filters. The main parameters affecting extractionperformance were investigated and optimized. Under the optimized conditions, the calibration graphs were linear over the range of 0.1-200 ?g·L-1. The limits of detection of the proposed method were 0.052-0.084?g·L-1(S/N=3). The single fiber repeatability varied from 5.18% to 7.56% and the fiber-to-fiber reproducibility ranged from 6.74% to 8.83% for the extraction of spiked water with 50 ?g·L-1 UV filters(n=5). The established SPME-HPLC-UV method was successfully applied to the selective concentration and sensitive determination of target UV filters from real environmental water samples with recoveries from 85.8% to 105% at the spiking level of 10 ?g·L-1 and 30 ?g·L-1. The relative standard deviations were below 9.67%.Chapter 3: The scanning electron micrograph of the Zn-Zn O coated fiber exhibits a porous spongy nanostructure with high surface area. The SPME performance of the prepared fiber was investigated for the concentration and determination of polycyclic aromatic hydrocarbons, phthalates and ultraviolet(UV)filters coupled to high performance liquid chromatography with UV detection(HPLC-UV). It was found that the porous sponge-like Zn-Zn O coating shows high extraction capability, good selectivity and rapid mass transfer for some UV filters.The main parameters affecting extraction performance were investigated and optimized.Chapter 4: A novel organic-inorganic composite coated fiber was developed by direct electrodeposition of rock-like Zn O followed by self-assembly of mercaptoundecanol using an etched stainless steel(ESS) wire as a supporting substrate for selective solid-phase microextraction(SPME). As a result, a uniform Zn O coating with rock-like structure was formed on the ESS wire and used as an alternative substrate for self-assembly of mercaptoundecanol(HS-C11-OH) via Zn-S bonding. The mercaptoundecanol modified Zn O coated ESS(ESS/Zn O-S-C11-OH)fiber was then assessed for SPME of ultraviolet(UV) filters, phthalic acid esters and polycyclic aromatic hydrocarbons(PAHs) coupled to high-performance liquid chromatography with UV detection. This fiber exhibits higher extraction capability and better selectivity for PAHs. Influential parameters of extraction, including desorption time, temperature, stirring rate and ionic strength, were investigated and optimized.