Determination of trace palladium(II) by catalytic kinetic spectrophotometry with potassium periodate and arsenazo I

A new kinetic spectrophotometic method for the determination of palladium(Ⅱ) is established,based on catalytic effect of palladium(Ⅱ)on the oxidation reaction of arsenazo Ⅰ by potassium periodate in the medium of phosphoric acid.When thiourea as activator is added,a stable complex comes into being and the catalytic reaction is obvious improvement.Under the selected conditions,a good linear relationship is obtained between the difference of absorbance of the uncatalytic and catalyytic systems at 502 nm and the concentration of palladium(Ⅱ)in the range of 0-0.60 μg/mL.The detection limit is 4.24×10-8g/mL.The apparent rate constant and the apparent activation energy of reaction found by determination of kinetic parameters of the catalytic reaction are 1.18×10-4s-1 and 71.13 kJ/mol respectively.This method has been used in the determination of palladium-catalyst and active carbon with the relative standard deriation from 0.47% to 1.74%.