Kinetic spectrophotometric determination of trace thallium(III) based on the discoloring reaction of arsenazo M by oxidation of potassium bromate

Based on the catalytic effect of trace thallium(III) on discoloring reaction of arsenazo M with potassium bromate in 0.08 mol/L sulphuric acid solution, a method for the determination of trace thallium(III) by kinetic spectrophotometry was established. The factors such as acidity, concentration of reactants, reactive time, temperature, influence of coexisting ions on the reaction and the optimum conditions of reaction and some kinetic parameters were determined. The apparent activation energy of the reaction is 70.12 kJ/mol. The detection limit is 0.17 μg/L and the linear range of determination is 0-20 μg/L for thallium(III). The relative standard deviation for the determination of 0.5 μg thallium(III) in 25 mL solution is calculated to be 3.4% (n=ll). Combined with solvent extraction separation, the method has been applied to the determination of trace thallium(III)in waste water and soil samples with the recovery of 97.0%-103.0%.