Determination of Trace Cerium by Catalytic Kinetic Spectrophotometry withLight Green SF and Potassium Periodate

A new catalytic kinetic spectrophotometry for the determination of trace cerium has been established.The method is based on the catalytic effect of trace cerium(Ⅳ) on the oxidizing discoloring reaction of light green SF with potassium periodate using thiourea as an activator in HAc-NaAc buffer solution at pH=4.5.The influence of medium,reagent dosage,reaction temperature,reaction time and coexisting ions on the determination were investigated.The detection wavelength was selected as 632 nm with optimal conditions.Under the optimal conditions,the apparent activation energy of the catalytic reaction was 91.2 kJ/mol.Most common ions did not interfere in the determination.There was a good linear relationship between the concentration of Ce(Ⅳ) and lg(A0/A) in the content range of 0 to 0.18 μg/mL.The detection limit of this method was 5.04×10-10 g/mL.The proposed method was applied to the determination of trace cerium in grain samples.The relative standard deviation was less than or equal to 7.65%(n=6),and the recoveries of standard addition were 94.4%～103.3%.The method is simple,sensitive,and accurate.The accuracies of the experiment meet the requirements for common grain sample analysis.