A catalytic spectrophotometric method based on the catalytic effect of Pt(Ⅳ) on the oxidation of 2-(4-chloroe-2-phosphonophenylazo)-7-(4-acetylphenlazo)-1, 8-dihydroxy-3, 6-naphthalenedisulfonicacid(chlorophosphonazo-pA) with KIO 4 in acidic medium has been proposed for the determination of trace platinum. The reaction is performed directly in an aqueous solution and the optimal conditions are given. The detection limit is 5.0×10 -8 g/mL. The Beer′s law is obeyed in the range of 1.5×10 -7～3.0×10 -7 g/mL. The method has been applied to the determination of platinum in Pt-Pd ores with satisfactory results.
