A high-selectivity spectrophotometric reagent for determining platinum(IV)

The new reagent N-(m-Methylphenyl)-N'-(sodium p-aminobenzenesulfonate)-thio urea (MMPT) was synthesized and its structure was confirmed by elemental an alysis, IR, UV and (HNMR)-H-1 spectra. The apparent molar absorptivities of usual ions were determined and the chromogenic reaction with microamounts of platinum(IV) was studied in detail. In the medium of an HAc-NaAc buffer solution, MMPT can react with platinum(IV) to form a green soluble complex. The maximum absorbance of the complex is at 754.4 nm (epsilon (754.4) = 8. 58 x 10(4) L.mol(-1).cm(-1)) and 332.8 nm (epsilon (332.8) = 1.14 x 10(5) L .mol(-1).cm(-1)). Beer's law was obeyed for platinum concentrations in the range of 0 similar to 1.28 mg.L-1; the correlation coefficient was r = 0.99 95. At 754.4 nm, over 50 ions did not interfere with the reaction. It is on e of the simplest and most selective methods available. It was convenient a nd rapid and has been applied to the direct determination of Pt(IV) in ores and catalysts with satisfactory results. (C) 2001 Elsevier Science B.V. Al l rights reserved.