1979 Volume 28 Issue 11 Pages 685-690
A highly sensitive method for the spectrophotometric determination of palladium(II) with ο-hydroxyhydroquinonephthalein (Qn.Ph.) and low concentration of quaternary ammonium salts in the presence of methylcellulose (MC) have been developed. Qn.Ph. forms a pure cobalt blue complex with palladium(II) in a weakly acidic medium in the presence of low concentration of cetyltrimethylammonium bromide (CTAB) as a cationic surfactant and an excess of MC as a nonionic surfactant. The color of the palladium(II)-Qn.Ph. complex was very stable and was used for the spectrophotometric determination of palladium(II) in aqueous solutions of pH 5.0. The absorbance of the complex remained constant when the pH was adjusted from 4.7 to 5.5 with Walpole buffer solution. The maximum absorption wavelength of palladium(II)-Qn.Ph. complex in the presence of MC and low concentration of CTAB was 625 nm, and in the presence of excess CTAB was 580 nm against water. A calibration curve was linear up to 6 μg/10ml palladium(II) at 625 nm against water. The recommended procedure for the determination of palladium(II) is as follows. A sample containing (1.06.0) μg of palladium(II) is taken in a 10.0 ml measuring flask, then 1.0 ml of 0.5% MC solution, 1.5 ml of 1.0×10-3 M CTAB solution, 2.0 ml of Walpole acetate buffer solution and 0.5 ml of 1.0×10-3 M Qn.Ph. methanol solution are added. The whole volume is brought to the mark with distilled water, and the solution is kept at 60°C for 30 min, then the absorbance of Qn.Ph.-palladium(II) solution is measured at 625 nm against water. The effect of foreign ions on the absorbance of the complex were examined.Iron(II), copper(II), aluminum(III), chromium(III) etc. interfered, and then copper(II), aluminum(III) could be masked by the addition of citric acid solution. The mole ratio of palladium(II) : Qn.Ph. : CTAB in the complex was estimated to be 2 : 3 : 2 by the continuous variation method and the mole ratio method. The apparent molar extinction coefficient at 625 nm is 1.27×105. The recovery of this method is 94.4%100.2%. This method is applicable to the analyses of palladium(II) in the catalyzers of palladium black and palladium asbestos.
