Spectrophotometric determination of platinum(IV) in catalyst with 4,5-dibromo-2-nitro-phenyfluorone

The chromogenic reaction of 4,5-dibromo-2-nitro-phenyfluorone(DBON-PF) with platium(Ⅳ) was studied and a spectrophotometric method for the determination of platinum was established.In the presence of CPB/OP microemulsion medium and in HAc-NaAc buffer solution at pH 3.6,platinum(Ⅳ) reacted with DBON-PF to form a stable pink complex with a molar ratio of 1︰2.The maximum absorption wavelength of the complex is at 476 nm.The apparent molar absorptivity is 1.88×105 L·mol-1·cm-1.Beer's law is obeyed in the range of 0-14 μg/10 mL for Pt(Ⅳ) and the detection limit is 1.06×10-6g/L.The method has been applied to the determination of platinum in catalyst samples with the recovery from 97.6% to 105.0%,the relative standard deviation from 1.1% to 2.1%,and the results are in line with those obtained by atomic absorption spectrometry.