Application Of Single-Wall Carbon Nanotubes For Elemental Speciation

The traditional analysis method is usually used for the determination of the amount or the total concentration of elements. This could not meet the requirement of modern science and technology. The physical activity and biological toxicity of an element are closely related with its form.To evaluate the effects of elemental speciation on the environment ,ecosystem and the health of human beings , the development of a sensitive, reproducible and accurate method for speciation analysis is of great importance. For the speciation of element in real samples, an effective separation and preconcentration procedure is usually applied prior to the measurement step by instruments.Solid phase extraction , as an isolation technique for elemental speciation, has attracted considerable practical interest in comparison with traditional liquid-liquid extraction method because of its several major features: (i) simple operation; (ii) high efficiency; (iii) rapid separation speed;(iv) the combination with different instruments;and (v) the repeated use of preconcentration materials. It should be worth notice that in solid phase extraction, adsorbent material plays a fundamentally crucial role in the improvement of the analytical performances for a method. For this reason, the extensive research and exploration of new adsorbents for solid phase extraction is a promising.Nanometer material is a new function material that has attracted a wide spread attention in the last few years for its special properties such as large specific surface area , surface energy and surface binding energy. Carbon nanotubes have large diameter ratio and large surface area. The surface atoms are unsaturated and can bind with other atoms easily,have highly chemical activity.Accordingly,carbon nanotubes can adsorb metal ions with high adsorption capacity. These facts imply that carbon nanotubes may be an ideal adsorption material for SPE of the analysis of trace elements.It is known to us that inductively coupled plasma mass spectrometry (ICP-MS) represents one of the most important routine methods for the determination of element and its speciation in various samples owing to its excellent analytical feature of rapid multi-element detection capability with high sensitivity . The purpose of this work is to investigate a microcolumn packed with single-walled carbon nanotubes(SWNTs) combined with ICP-MS for the analysis of the elemental speciation in environmental and biological samples . The following contents are included in this work.(1) Based on single-wall carbon nanotubes (SWNTs) as a new adsorbent material,a procedure was proposed for simultaneous separation and speciation of inorganic As (III) and As(V) by solid phase extraction coupled with ICP-MS in the presence of APDC.The adsorption behaviors of As(III) and As(V) on SWNTs and the affecting factors were investigated in detail . The proposed method was applied to the determination of As(â…¢) and As(â…¤) in real samples.(2) The adsorption property of Mn(II) and Mn(VII) on SWNTs was investigated by ICP-MS, respectively. The experimental parameters,including pH , sample flow rate and volume , elution solution and interfering ions on the recoveries of the analytes were optimized. The recommended approach was applied for the determination of trace/ultra-trace Mn(II),Mn(VII),and total Mn in natural water samples.(3) A new kind of adsorbent of SWNTs was developed for the separation, preconcentration and determination of inorganic chromium speciation by ICP-MS. The key factors, such as adsorption rate, pH, sample solution flow rate, elution solution, volume and interfering ions on the determination of Cr(III) and Cr(VI) were examined in detail. The Cr(III) and Cr(VI) in real samples were determined by the proposed method, and the good results were obtained.