Catalytic kinetic spectrophotometric determination of trace rhodium with Rh(III)-kIO_4-malachite green system

In hydrochloric acid and at 95 ℃ rhodium(Ⅲ) can catalyze the depigmentation reaction of potassium periodate oxidizing malachite green.The optimal experimental conditions have been discussed and based on the optimal experimental conditions a new method of catalytic kinetic spectrophotometric determination of rhodium has been established.The absorbency difference ΔA and the concentration of rhodium(Ⅲ) remains good linear relationship in 0.04～0.06 μg/mL,and the detection limit is 5.98×10-10 g/mL.The dynamic parameter is also measured,suggesting that this reaction is a first order reaction.The apparent rate constant is 7.67×10-4 s-1,and the apparent activation energy is 58.20 kJ/mol.The method has been applied to the determination of trace amount of rhodium in molecular sieve catalysts and active carbon and resulted with a recovery rate between 95.8% to 106.6% which meets the requirement of trace amount analyst determination.