Study of Solid Phase Extraction Prior to Spectrophotometric Determination of Platinum with N-(3,5-Dimethylphenyl)-N′-(4-Aminobenzenesulfonate)-Thiourea

Abstract.

A highly sensitive, selective and rapid method for the determination of platinum based on the rapid reaction of platinum(IV) with N-(3,5-dimethylphenyl)-N′-(4-aminobenzenesulfonate)-thiourea (DMMPT) and the solid phase extraction of the Pt(IV)-DMMPT complex with C₁₈ membrane disks was developed. In the presence of pH = 3.8 buffer solution and cetyl trimethylammonium bromide (CTMAB) medium, DMMPT reacts with platinum to form a violet complex of a molar ratio of 1:3 (platinum to DMMPT). This complex was enriched by solid phase extraction with C₁₈ membrane disks, and an enrichment factor of 200 was obtained. The molar absorptivity of the complex is 9.51 × 10⁴ L · mol⁻¹ · cm⁻¹ at 755 nm, and Beer’s law is obeyed in the range of 0.01–3.0 µg mL⁻¹ in the measured solution. The relative standard deviation for eleven replicate samples of 0.01 µg mL⁻¹ level is 1.79%. The detection limit reaches 0.02 µg L⁻¹ in the original samples. This method was applied to the determination of platinum in water and soil samples. The relative standard deviations are 2.9–3.4%. The recoveries are 94–105%. The values of determination obtained agree with those of the ICP-MS method. The results are satisfactory.