Catalytic kinetic spectrophotometric determination of trace rhodium with rhodium-potassium periodate-fast green FCF system

In potassium hydroxide,trace rhodium(Ⅲ)could catalyze fading reaction of periodate potassium oxidizing fast green FCF(FG)in boiling bath for 13 min,based on which a novel method for catalytic kinetic spectrophotometric determination of trace rhodium was established.The optimal conditions of catalytic reaction and the kinetics parameters were discussed.It was found that,the concentration of rhodium showed a good linear relationship with the absorbance difference(ΔA)of the catalytic and non-catalytic reaction within the range of 1-12ng/mL,and the correlation coefficient(r)was0.998 9.The detection limit was 9.52×10-11 g/mL.The apparent rate constant was 6.97×10-3/s and the apparent activation energy was 71.08kJ/mol.The method has been applied to determine rhodium in catalysts of rhodium-carbon and platinum-rhodium.The results were basically consistent with those obtained by stannous chloride spectrophotometry.The relative standard deviation(RSD,n=6)was 2.4%-3.6%,and the standard addition recovery was 99%-102%.