Studies And Applications Of The Separation And Preconcentration Of Trace Elements With Nanometer Titanium Dioxide And Determination By Atomic Absorption Spectrometry

The atomic adsorption spectrometry (AAS), which has the merits of low cost and detection limit, good precision and accuracy, and wide linear range, has been widely applied in trace analysis.By coupling solid-phase extraction (SPE) with AAS, the analytical performance of the analytical method, such as sensitivity, detection limit and selective capability could be efficiently improved. At the same time, it also extends the application field of SPE. And the choice of adsorb materials is the decisive factor that affects analytical sensitivity and selectivity.Nanometer material is a new function material that gained development and importance in recent years. Nanometer materials are made of nanometer particles, the regime of particle is from 1 nm to 100 nm, falls between the classic fields of chemistry and solid-state physics. The sizes, surface structures and particles interactions of nanometer materials determine their unique properties and the improved performances. 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.In this paper, the self-made nanometer TiO₂ was applied in field of analytical detemination, and the adsorption characteristics of some trace elements on nanometer TiO₂ material was systematically studied with AAS.A novel method was developed for determination of trace elements such as Pb, Au, La, which combined AAS with separation/preconcentration by nanometer TiO₂ with good stability and high selectively, sestively and pollution-free. The major contents are described as follows:1. The methods of separation/preconcentration and kinds of adsorption materials in atomic adsorption spectrometry detemination were reviewed. The characteristics and application in separation/preconcentration of new adsorption material- nanometer material were introduced in detail.2. The samples of nanometer TiO₂ of uniform particle diameter were prepared by improved Sol-Gel method. Then, the product was to be determined by TEM. It was found that the product is nanometer TiO₂. There is little agglomeration and the particle diameter is in the 10～30 nm region. So it is suitable for solid phase adsorbent. The adsorption characteristics of heavy metal ions Pb2+ on nanometer TiO₂ under static condition were studied, and the conditions such as sorption kinetics, effect of pH on adsorption ratio, and adsorption capacity for preconcentration of trace elements were optimized. The proposed method has been applied for the determination of trace Pb in water samples with satisfactory results. The recoveries of Pb2+ ranged from 94.5% to 102.5%. The detection limit of this method for Pb2+ was 2.57 ng/mL, and relative standard deviation was 2.45% (n=11, c=0.10μg/mL).3. The adsorption characteristics of precious element Au on supported nanometer Ti02 under dynamic condition were studied. Selective preconcentration of gold was obtained at pH=3.5. The linear range for gold was 0⁰.40μg/mL ,A=1.755C+0.0205(C:μg/mL,r=0.9993),detection limit(3σ, n=11) of this method for gold was 2.34 ng/mL; And the relative standard deviation for gold was 2.9% (n=6, c=0.10μg/mL). The method has been applied for the determination of trace gold in water samples with satisfactory results. The recovery was in the range of 96.7% to 101.7%.4. A PTFE micro column packed with 1-phenyl-3-methyl-4-bonzoil-5-pyrazone (PMBP) on nanometer TiO₂ was used in FI (flow injection)-FAAS (flame atomic adsorption spectrometry) system for the determination of trace La. The adsorption characteristics of rare earth element La on nanometer Ti02 under static condition were studied, and the conditions for preconcentration of this element were optimized. The method has been applied for the determination of trace La in environmental and biological samples with satisfactory results.