Use Of Titanium Dioxide Nanotubes For Separation And Preconcentration Of Trace Elements Prior To Their Determination By Inductively Coupled Plasma Mass Spectrometry

With the rapid development of economy in our country, environment pollution caused by metals, especially heavy metals, has received considerable attention in recent years. Therefore, it is very required to develop a fast, sensitive and reliable method for the determination of trace elements in environmental and biological samples. However, the direct determination of trace/ultra-trace elements in biological and environmental samples by existing instruments often suffers from the following problems:(i) extremely low concentration,(ii) complicated sample constituent, and(iii) remarkable matrix effects. In order to achieve an accurate and reliable analytical result, an effective separation and preconcentration technique is usually mandatory before analysis.Sold phase extraction(SPE), as one of the most effective preconcentration and separation methods, has aroused considerable interesting because it reduces consumption and exposure to organic solvents, as well as decreasing the amount of solvent which need to be disposed. SPE is also less time-consuming than liquid-liquid extractions, and it can provide more flexible working conditions and simple operation. It is worth noting that the adsorbent is crucial for achieving the good selectivity and sensitivity. Thus, the development of a new adsorbent material with high selectivity and sensitivity is forever of interests to analysts. In recent years, nanometer-size materials have drawn growing attention in analytical sciences because of their special properties. One of them is that most of the atoms of nanoparticle are on the surface. The surface atoms are unsaturated, possess highly chemical activity, and can easily bind with other atoms. Consequently, interest in adapting nanometer material as a new adsorbent for the preconcentration and separation of substance has increased significantly.Titanium dioxide nanotubes(TDNTs), as an interesting member of nanomaterials, have much higher adsorption capacity than that of TiO2 nanoparticles because they have been shown to have large surface area, which makes them promising candidates as adsorbers. However, to the best of our knowledge, the studies on the application of TDNTs for the determination of trace elements have received little attention so far. The aim of this dissertation is to systematically investigate the adsorption characteristics of the metal ions on TDNTs by ICP-MS, and apply it to the separation/preconcentration of trace elements in biological and environmental samples. The major contents are described as follows:(1) Based on TDNTs as the adsorbent of solid phase extraction, the adsorption characteristics of heavy metal element Tl was studied by ICP-MS. The main parameters for separation and preconcentration of Tl such as pH, sample flow rate, sample volume, interfering ions and elution conditions were examined in detail. A new method was described for separation/preconcentration and determination of trace Tl in environmental samples.(2) The adsorption behaviors of metal Au on TDNTs was investigated by a microcolumn packed with TDNTs coupled by ICP-MS. The main factors affecting the separation, preconcentration and determination of the analyte were also examined in detail. The proposed method has been applied to the analysis of biological and environmental samples.