Study On Separation/Preconcentration Of Trace Element With Single-Walled Carbon Nanotubes

With the rapid development of modern science and technology, there is an increasing demand for the information about the ingredient,species and structure of substances. In spite of the great improvement of instrumental power of detection at present ,direct determination of trace elements in extremely low concentration by modern analytical techniques is,in many cases, difficult.This is not only due to the insufficient sensitivity of the methods, but also the matrix interferences. To overcome these difficulties,the preliminary separation/preconcentration methods are still frequently required prior to the analysis for the improvement of sensitivity, selectivity and accuracy of analytical method.Solid-phase extraction(SPE) technique has become increasingly popular in trace elements separation/preconcentration due to its advantages of simple to operate, high preconcentration factor, low consumption of organic solvents, rapid phase separation and the ability of combination with different detection techniques. It should be pointed out that the choice of adsorbents for solid-phase extraction is decisive factor that affects analytical sensitivity and selectivity. Therefore, it has still been a very interesting research field to find new and effective adsorbentsNanometer material is a new function material that gained development and importance in recent years because of its special properties such as large specific surface area, surface energy and surface binding energy. One of the specific properties is that a high percent of the atoms of the nanometer particle is on the surface. The surface atoms are unsaturated and can therefore bind with other atoms easily, possess highly chemical activity. Consequently, nanometer materials can adsorb metal ions with high adsorption capacity. These facts imply that nanometer-size material may be a promising adsorption material for solid-phase extraction.As is well known, inductively coupled plasma mass spectrometry (ICP-MS)has become one of the most effective techniques for the determination of trace/ultra-trace elements due to its low detection limits, super high sensitivity,broad dynamic linear range and rapid multi-element detection capability. The aim of this dissertation is to systematically study the adsorption characteristics of the metal ions on single-walled carbon nanotubes by ICP-MS, and apply it to the separation/preconcentration of trace elements in real samples. The major contents are described as follows:(1) The adsorption behaviors of trace Cu, Co and Pb on single-walled carbon nanotubes were studied. The effects of pH, sample flow rate and volume, elution solution and interfering ions on the preconcentration and separation of analytes were examined in detail. The proposed method was applied to the preconcentration/separation and determination of trace Cu,Co and Pb in biological and environmental samples.(2) The adsorption characteristics of rare earth elements on single-walled carbon nanotubes(SWNTs)were studied, and the conditions for preconcentration/separation of trace elements were optimized and selected in detail. On the basis of the obtained experimental results, a new method of SWNTs preconcentration coupled with ICP-MS for simultaneous determination of rare elements in biological and environmental samples. was proposed.(3) A novel method was developed for the preconcentration of trace gold and palladium with a microcolumn packed with single-walled carbon nanotubes under dynamic conditions prior to their determination by ICP-MS. The conditions of preconcentration were investigated. The proposed method was applied to the analysis of gold and palladium in geological samples.