Study On The Application Of Cloud Point Extraction In Speciation Analysis Of Heavy Metal Ions

The rapid development of economy results in the stead increase of heavy metal consuming and draining off. The polluting by heavy metals is becoming more and more and comprises an important factor influencing the people's healthy and social economic development of our country. Therefore, the separation and preconcentration and determination of trace heavy metals are the research content of analytical scientists.Cloud point extraction (CPE) is a kind of new environmentally benign liquid-liquid extraction method. The technique is based on the property of most non-ionic surfactants in aqueous solutions to form micelles and become turbid when heated to a temperature known as the cloud point temperature. Above the cloud point, the micellar solution separates into a surfactants-rich phase of a small volume and a diluted aqueous phase, in which the surfactant concentration is close to the critical micellar concentration (CMC). Any analyte solubilized in the hydrophobic core of the micelles will separate and become concentrated in the small volume of the surfactant-rich phase. The small volume of the surfactant-rich phase obtained with this methodology permits the design of extraction schemes that are simples, economical, highly efficient, speedy, and of lower toxicity to the environment than those extractions that use organic solvents. Separation and preconcentration based on cloud point exraction is becoming an important and practical application in the use of surfactants in analytical chemistry. It's widely used in the separation and purification of bio-molecules and extraction of compounds and metal ions.The aim of this dissertation is to systematically study on the joining technique of High performance liquid chromatography inductively coupled plasma mass spectrometry(HPLC-ICP-MS) and the cloud-point extraction, and their application to the separation/preconcentration and speciation of metal ions. The major contents are described as follows:1. A new method for the determination of trace mercury species in water samples by High performance liquid chromatography inductively coupled plasma mass spectrometry after cloud point extraction was proposed. The effect of experimental conditions such as pH, concentration of chelating agent and surfactant, equilibration temperature and time on cloud point extraction was studied. The method was successfully applied to the determination of MeHg+ and Hg2+ in water and biological samples, and the achieved detection limits were 10 and 4 ng/L for MeHg+ and Hg2+, respectively. 2. A new method for the determination of trace thallium in water samples by electrothermal atomic absorption spectrometry after cloud point extraction was proposed. Atomization behaviors of thallium and influences on the spectral background by the diluted surfactant solution introduced into the graphite furnace tube were studied. The effect of experimental conditions such as pH, concentration of chelating agent and surfactant, equilibration temperature and time on cloud point extraction was studied. The chemical variables affecting the separation and extraction recovery were optimized. The method was successfully applied in determination of trace thallium in drinking water, tap water and river water, and the detect limit was 0.07μg/L.