Spectrophotometric method for the rapid determination of microgram amounts of platinum

Abstract

10-[3-(4-Methyl-1-piperazinyl)propyl]phenothiazine dimalonate (perazine) forms a yellowish brown complex with platinum(IV) at room temperature (27 ± 1 °C) in orthophosphoric acid medium containing copper as catalyst. The complexation is complete within 1 min. The complex exhibits an absorption maximum at 512 nm with a molar absorptivity of 1.6 × 10⁴ 1 mol^–1 cm^–1. Beer's law is valid over the concentration range 0.4–6.8 p.p.m. A 50-fold molar excess of the reagent is necessary for the full development of the colour intensity. Calculations by Job's method of continuous variation, the molar-ratio method and the slope-ratio method indicate a 1 + 1 composition for the complex. The effects of acidity, time, temperature, reagent concentration, order of addition of reagents and the interferences of various ions are reported. The reagent has been used successfully for the determination of platinum in minerals and alloys.