Study On The Speciation Analysis Of Element With Carbon Nanofibers

With the development of environmental science and biological science, there is an increasing demand for the information about speciation because the different chemical forms of an element have different effects on human health, the environment and the ecosystems. Therefore, the separation and determination of elemental species is of great importance. In general, in order to obtain the data about the chemical form of elements, the separation and preconcentration are usually required before analysis by instruments.Solid phase extraction(SPE) as a separation and preconcentration technique has become increasingly popular in the pretreatment of samples 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. The choice of adsorbents for SPE is very important as it is decisive and direct factor that affects analytical sensitivity and selectivity. Therefore, it has still been an interesting research field to find new and effective adsorbents nowadays. Carbon nanofibers(CNFs), as a novel and interesting carbon material, have very attractive features:small size, large specific surface area, excellent mechanical strength, highly chemical stability, and unique electrical property. Their surface properties can be modified through different treatments to satisfy special needs. These make them a promising candidate as adsorbers for solid phase extraction. As is well know, inductively coupled plasma mass spectrometry (ICP-MS) has become one of the most appropriate 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 use a microcolumn packed with CNFs coupled to inductively coupled plasma mass spectrometry (ICP-MS) for the speciation analysis of elements in real samples. The major contents are described as follows:(1) The adsorption characteristics of Cr(â…¢) and Cr(â…¥) on CNFs were investigated systematically. Based on the obtained results,a novel method was developed for the speciation of chromium by a microcolumn packed with CNFs as adsorbent coupled with ICP-MS. The proposed method has been applied to the determination of the chromium in certified materials, and chromium species in water samples with satisfactory results.(2) The adsorption behaviors of Mn(â…¡) and Mn(â…¦) on CNFs under dynamic conditions were studied systematically. The main factors influencing preconcentration and determination of the analytes have been examined in detail. A novel method with carbon nanofibers(CNFs) as a solid phase extraction adsorbent for the preconcentration and determination of Mn(â…¡) and Mn(â…¦) was developed by inductively coupled plasma mass spectrometry (ICP-MS) detection.(3) A new method for the separation/preconcentration of As(â…¢) and As(â…¤) with a microcolumn packed with carbon nanofibers is described for the determination by inductively coupled plasma mass spectrometry in the presence of APDC. The effects of pH, sample flow rate and volume, elution solution and interfering ions on the adsorption of analytes were examined in detail. The proposed method was applied to the determination of As(â…¢) and As(â…¤) in real samples with good results.