Determination And Speciation Of Thallium By Platform-GFAAS After Preconcentration With Polyurethane Foam

Thallium (Tl) is a non-essential and toxic element. This rare metal is widely distributed in environment. It was known that Tl had caused many acute and chronic intoxication accidents in history. There has been an urgent need for the determination of thallium.A method for the determination and speciation of thallium was developed in this dissertation. The parameters for the adsorption, such as adsorbing medium, elution and oxidation and for the determination were optimized. Thallium, either Tl(â…¢) or oxidized jto Tl(â…¢) was complexed with Cl~- and absorbed by several pieces of polyurethane foam. The optimal adsorbing medium was 20% HCl. The adsorbed thallium could be eluted quantitatively in boiling water for 10 to 15min. The content of thallium in elute was assayed by platform-GFAAS. It was found that some common matrix modifiers did not improve thallium determination and perchlorate depressed the signal of thallium severely. In optimal condition the characteristic concentration was 2ng/L. The proposed method was applied to the determination of thallium in tap water, river water and mineral water with the recovery ranged from 85.7% to 101.0%. Dilute bromine water as oxidant, the speciation was also achieved successfully.Tl in urine is a sensitive index for its body exposure and correlative to the degree of intoxication. Low content of Tl and high content of inorganic salts in urine of healthy people made it difficult for direct determination with GFAAS. It was necessary to digest the organics and separate the analyte from the matrix before determination. Several kinds of digest method, for example, digest with dilute bromine water, aqua regia and a mixture of nitric acid and perchloric acid or a mixture of nitric acid and sulfuric acid were tested. Finally, the mixture of nitric and sulfuric acid was chosen to digest urine since it gave best recovery. Through proposed procedure, the interference from inorganic salts could be eliminated and Tl could be concentrated. The characteristic concentration was 0.02ng/L and the recoveries ranged from 92.7% to 97.7%. The proposed method was applied to analyze 21 urine samples, and these healthy men's 95% CI was( 0.29, 0.48) ug/L. Urine Tl of three acute intoxication patient also has been determined. The detoxification efficiency of prussian blue were certified.