Spctrophotometric Determination of Trace Ruthenium by its Catalytic Effect on Oxidation of 3,5-DiBr-PADAP with KIO4

Abstract

A spectrophotometric method for the determination of ruthenium (III) is described, based on its catalytic effect on the oxidation reaction of 2-[(3,5-dibromo-2-pyridy)azo]-5-diethylaminophenol (3,5-diBr-PADAP) with potassium periodate in 0.008 mol/L sodium hydroxide medium and in the presence of OP emulsifier (p-iso-octyl phenoxy polyethoxy ethanol) at 100 °C. The above reaction is followed spectrophotometrically by measuring the decrease in the absorbance at 530 nm for the catalytic reaction of 3,5-diBr-PADAP. The calibration curve for the recommended method was linear in the concentration range over 0.04 µg/L–1.0 µg/L and the detection limit of the method for Ru (III) is 0.012 µg/L. The influence of the factors such as acidity, concentration of reactants, reaction time, temperature and co-existing ions on the reaction is discussed. The optimum conditions of reaction are established and some kinetic parameters are determined. The apparent activation energy of catalytic reaction is 100.48 kJ/mol. The relative standard deviation for the determination of ruthenium (III) at the concentration of 0.02 µg/25mL is calculated to be 2.30 % (n=11). In combination with distilled separation, the method has been successfully applied for the determination of trace ruthenium (III) in some ores and metallurgy products with the relative standard deviations (RSD) over 1.8 %–2.9 % and the recovery over 98.1 %–103.1 %.