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

The new reagent N-(m-Methylphenyl)-N′-(sodium p-aminobenzenesulfonate)-thiourea (MMPT) was synthesized and its structure was confirmed by elemental analysis, IR, UV and 1HNMR 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 (ε754.4=8.58×104 L·mol−1·cm−1) and 332.8 nm (ε332.8=1.14×105 L·mol−1·cm−1). Beerʹs law was obeyed for platinum concentrations in the range of 0∼1.28 mg·L−1; the correlation coefficient was r=0.9995. At 754.4 nm, over 50 ions did not interfere with the reaction. It is one of the simplest and most selective methods available. It was convenient and rapid and has been applied to the direct determination of Pt(IV) in ores and catalysts with satisfactory results.