Determination of trace iridium(IV) by catalytic kinetic spectrophotometric method with KIO_4-crystal violet system

On the basis of strongly catalytic action of iridium on the discoloring reaction of crystal violet and potassium periodate in H2SO4 at 95℃,a new method for using catalytic kinetic spectrophotometry to determine trace iridium (Ⅳ) has been developed.Under selected experimental conditions,the absorbency difference ΔA between the catalytic reaction and noncatalytic reaction remains in a good linear relationship to the mass concentration of iridium(Ⅳ) between 0.006~2.00 μg/ mL with the detection limit of 3.2×10-10 g/mL.The kinetic parameters of the catalytic reaction were determined and the reaction was a pseudo first order one.The apparent rate constant of the reaction is 5.116 7×10-4 /s,and the apparent activation energy is 55.03 kJ/mol in 95℃.The proposed method is applied to the determination of iridium in molecular sieve catalyst and active carbon with the recovery rate between 94.6%-108%.