Determination of trace rhodium by potassium bromate-safranine O inhibition kinetic spectrophotometry

In 1.0 mol/L sulfuric acid medium and hot water bath at 95 ℃, trace rhodium  had strong inhibition action on the fading reaction of safranine O oxidized by KBrO3. Based on this, a new determination method of trace rhodium  by inhibition kinetic spectrophotometry was established. Moreover, the related kinetic parameters were measured. Under the selected experimental conditions, the linear range of method was 0.2-0.8 ng/mL, the detection limit was 1.93×10-11 g/mL, and the apparent activation energy was 118.2 kJ/mol. The inhibition reaction was first order reaction for both sulfuric acid and rhodium. The proposed method was applied to the determination of rhodium in catalyst. The found results were consistent with those obtained by SnCl2 photometry. The relative standard deviations (RSD) were 2.7% and 2.9%.