Studies On New Methods For Elements And Speciation Anlysis By Cloud Point Extraction Coupled With Atomic Absorption Spectrometry

Atomic absorption spectrometry (AAS) is one of widely uesd techniques for determination of trace elements in all kinds of samples. Although AAS is an effective element detector with relatively high sensitivity and selectivity, direct analysis trace elements in different samples becomes a difficult and impossible task. Because the sample matrix is more and more complicated and analyte is often at trace or ultrace level with the development of analytical chemistry. Therefore, it is necessary that some kinds of sample preparation techniques must be involved prior to determination, which separates analyte and sample matrix and concentrates the analyte for better sensitivity and selectivity.Due to consumption of large amounts of toxic organic reagents, tedious and time-consuming operations, the traditional liquid-liquid extraction methods have failed to meet the needs of the development of green analytical chemistry, and there is the great need of new separation/preconcentration techniques to meet the development. Recently, cloud point extraction (CPE) as a new liquid-liquid extraction technique has been widely accepted. It is based on the cloud point phenomenon of surfactant and micellar solution solubilization. Compared with traditional liquid-liquid extraction, CPE offers some advantages including wide range of application, high enrichment factor, safety and environment friendly, simple operation and ease of hyphenation with other instruments. CPE has been widely used in separation and enrichment of trace elements, organic pollutants, and biological macromolecules as well as active ingredients of drugs.The combination of CPE separation and preconcentration and AAS determination for trace elements and speciation analysis could improve the selectivity and selectivity of the analytical method. The aim of this dissertation is to combine CPE with AAS detection, and sysmatically study on the factors (including pH, chelating agent and surfactant concentration, equilibrium temperature, incubation time and effect of coexisting ions) affecting CPE and its application to the separation/preconcentration trace elements and their speciation in different food samples. The major contents are described as follows:(1) A method for the separation/preconcentration of trace cadmium by cloud point extraction prior to ETAAS was developed. The variables affecting the extraction efficiency of cadmium were optimized. And the proposed method was applied to the determination of trace cadmium in rice, purified water and liquor samples. (2) A method for speciation analysis of antimony(III) and antimony(V) by ETAAS after CPE was studied. The parameters effecting the extraction efficiency of antimony(III) and the condition for selective extraction of antimony(III) and antimony(V) were investigated. The proposed method was applied to speciation analysis of antimony(III) and antimony(V) in different food packing materials.(3) A new method for determination of trace cadmium by FAAS after CPE was established, which was based on Triton X-114 as surfactant and formation of Hydrophobic ion-association complex between methyl green (MG) and CdI42-. Several factors affecting extraction efficiency of cadmium were investigated respectively. The proposed method was applied to the determination of trace cadmium in rice, laver and kelp samples.