Catalytic kinetic spectrophotometric determination of trace cerium IV with azure I-potassium periodate-Triton X-100 system

A new catalytic discoloring kinetic spectrophotometric method for the determination of the trace Ce Ⅳ was studied.The method was based on the catalytic effect of cerium Ⅳ on the oxidation of azure I by KIO4 in the presence of non-ionic surface of Triton X-100 as sensitizer and in H3PO4 medium.The effects of absorption spectra,acidity,concentrations of reagent,and the influence of coexistence ions on the reaction were discussed,and the kinetic conditions were studied.Under the optimum conditions,the linear range of the method was 0-80 μg/L.The detection limit was 4.58×10-7 g /L.The catalytic reaction was the zeroth order one.The apparent activation energy and the reaction rate constant was found to be 96.04 kJ/mol and 3.61×10-3/s,respectively.The sensitivity was increased by 3 times in the presence of surfactant.The method was used in the determination of cerium in rare earth oxides,with the relative standard deviation below 2.5% and the average recovery of 100%-103%.