Studies On The Separation And Preconcentration Of Trace Metals By Cloud-Point Extration And Determination With AAS

With the development of science and technology, sensitive, rapid, reproducible, simple and accurate analytical methods are required for the determination of trace elements in geological, biological and environmental samples. The direct determination of extremely low concentration of trace element with modern atomic spectroscopic method, such as atomic absorption spectrometry (AAS) is so difficult. On one hand, the limitations are associated not only with the insufficient sensitivity of these techniques but also with matrix interference. That's the reason why the separation and preconcentration of trace elements is often required.Cloud point extraction (CPE) is related to the conventional liquid-liquid extraction (LLE). CPE based on the solubility and cloud point phenomenon of aqueous solutions of surfactants, upon alteration of the experimental conditions such as pH value of solution, ionic strength, temperature, and the solution is separated into phases, which results in the separation of hydrophobe and hydrophile. CPE is an easy, safe, high efficiency and inexpensive methodology for separation and preconcentration. It has been widely used in the study of life sciences and environment sciences, and has also been successfully used in the separation and preconcentration of mental element.The atomic absorption spectrometry (AAS), which has the merits of low price and detection limit, good precision and accuracy, and wide linear range, has been widely applied in trace analysis. By coupling CPE with AAS, the analytical performance of the analytical method, such as sensitivity, detection limit and antijamming capability, could be efficiently impoved.The aim of this paper is to systematicaly study on the cloud-point extraction and its application to the separation/preconcentration of metal ions. The major contents are described as follows:Based on the principle and application of cloud point extraction,analysized prevous achievements and current situation in the research of cloud point extraction, and proposed the ideas of this paper.A new method for the determination of trace palladium by flame atomic absorption spectrometry after cloud point extraction was proposed. The effects of experimental conditions such as pH, concentration of chelating agent and surfactant, equilibration temperature and time on cloud point extraction were discussed. Uunder the optimum conditions, the detection limit was 10.1 ng/mL, and the relative standard deviation was 2.12% (n=10). The recoveries of Pd2+ ranged from 97.6% to 105.9%. The proposed method has been applied to the determination of palladium in catalyst with satisfactory results.A new method for the determination of trace Gold by flame atomic absorption spectrometry after cloud point extraction was proposed. The effects of experimental conditions such as pH, concentration of chelating agent and surfactant, equilibration temperature and time on cloud point extraction were discussed. Under the optimum conditions, the detection limit was 7.9 ng/mL, and the relative standard deviation was 4.12% (n=11). The recoveries of Au3+ ranged from 97.5% to 102.8%. The proposed method has been applied to the determination of Gold in Mineral waste residue samples with satisfactory results.A new method for the determination of trace Silver by flame atomic absorption spectrometry after cloud point extraction was proposed. The effects of experimental conditions such as pH, concentration of chelating agent and surfactant, equilibration temperature and time on cloud point extraction were discussed. Under the optimum conditions, the detection limit was 1.69 ng/mL, and the relative standard deviation was 2.95% (n=11). The recoveries of Silver ranged from 98.4% to 103.9%. The proposed method has been applied to the determination of Silver in water samples with satisfactory results.A new method for the determination of trace Lead by flame atomic absorption spectrometry after cloud point extraction was proposed. The effects of experimental conditions such as pH, concentration of chelating agent and surfactant, equilibration temperature and time on cloud point extraction were discussed. Under the optimum conditions, the detection limit was 2.41 ng/mL, and the relative standard deviation was 3.74% (n=11). The recoveries of lead ranged from 97.4% to 102.3%. The proposed method has been applied to the determination of Lead in water samples with satisfactory results.