1-(2-Pyridylazo)-2-Phenanthrol (PAP) as an Extractive Chromogenic Reagent for Platinum(IV)

Abstract

Platinum(IV) forms a green complex with 1-(2-pyridylazo)-2- phenanthrol (ten fold excess) when heated on a boiling water bath for about 2 hours (pH 2.9 to 5.5). The complex is soluble in 75% ethanol, methanol and extractable in chloroform and shows maximum absorbance at 670 nm. Beer’s law is obeyed upto 7.943 ppm of platinum at 670 nm. The sensitivity of the method is 0.0283 μg Pt(IV)/cm² for log I₀/I = 0.001 and the molar extinction coefficient ε₆₇₀ = 8400 litre mole^-1 cm^-1. The composition of the complex is 1:1 as determined by Job’s method. The possibility of determining platinum(IV) in the presence of various diverse ions has also been investigated.