Selective Liquid–Liquid Extraction of Platinum(IV) from Ascorbate Media by N-n-Octylaniline: Its Separation from Associated Elements and Real Samples

Abstract

The distribution equilibrium of platinum(IV) species between aqueous ascorbate media and 0.1 mol/L of N-n-octylaniline in xylene was studied as a function of different parameters, such as the concentration of extractant in organic phase, weak organic acid concentration, different diluents, and effect of shaking period on extraction. The quantitative extraction of platinum(IV) was observed with N-n-octylaniline in xylene from 0.01 to 0.02 mol/L of ascorbic acid in the pH range of 0.5 to 1.25. The metal ion was stripped out from organic phase with water and determined spectrophotometrically with stannous chloride. The extraction of platinum(IV) was quantitative in most aromatic solvents, such as benzene, toluene, and xylene. The stoichiometry of the extracted species was determined on the basis of slope analysis and found to be 1:3:1 (metal:acid:extractant). As an application, the system was used for selective extraction of platinum(IV) from its binary mixture with Pd(II), Au(III), Rh(III), Ir(III), Os(VIII), Ru(III), Fe(III), Co(II), Ni(II), and Cu(II), and also from its ternary mixture with Pd(II) and Rh(III). The distribution coefficient for platinum(IV) in ascorbate media was of higher magnitude than malonate, salicylate, succinate, tartrate, acetate, and oxalate media. The method developed was successfully applied for the analysis of platinum(IV) in the real samples, such as platinum–rhodium thermocouple wire, pharmaceutical sample cisplatin, and catalysts.