Solid phase extraction and spectrophotometric determination of platinum in catalysts with p-rhodanineazo benzoic acid

Based on the color reaction of p-rhodanineazo benzoic acid(RABA)with platinum(Ⅳ)and the solid phase extraction of the colored complex with C_8 cartridge,a new method for the determination of platinum was developed.In the presence of sodium dodecyl benzenesulfonate (SDBS)and KOH-C_6H_4 (COO)_2 HK buffer solution(pH 4.0-6.2)medium,RABA reacts with platinum(Ⅳ)to form a stable 1:1 complex.The complex was enriched by AccuBond C_8 cartridge and is eluted from the cartridge with ethanol,then the eluant was determined by spectrophotometry.In the ethanol medium,the apparent molar absorptivity of the complex was 2.49×10~5 L·mol~(-1)·cm~(-1) at 520 nm.Beer's law was obeyed in the range of 0.1～1.0μg/mL for platinum.The condition of solid phase extraction was stud- ied.Interference from common ions and its elimination were discussed.The method was applied to de- termine trace platinum in the catalysts.The results were consistent with those obtained by AAS meth- od,with RSD of 1.9%—2.3%(n=7)and recovery of 97%—101%.