Sensitive flotation-spectrophotometric determination of platinum based on systems with chlorostannate(II) and basic dyes

Abstract

Sensitive flotation-spectrophotometric methods are based on the ion-associates formed by the anionic chlorostannate(II) complex of platinum with the basic dyes rhodamine 6G, Victoria blue B, Victoria blue 4R and Capri blue. The ion-associates finally formed are sparingly soluble in water; when shaken with a suitable organic liquid, they accumulate quantitatively at the phase boundary or on the wall of the separatory funnel. The compound with rhodamine 6G, separated and washed, is dissolved in acetone; those ones with the other basic dyes are dissolved in methanol. In the best method, with rhodamine 6G, the molar absorptivity is 2.8 × 10 5 l mol −1 cm −1; with the other dyes, the molar absorptivities are 2.0–2.45 × 10 5. Beer's law is obeyed over the range 0.08-0.6 μg Pt ml −1. The separated ion-associate formed with rhodamine 6G (R6G) is considered to have the formula [(R6G +) 3] [Pt(SnCl 5) 3- 5]. The effects of other platinum metals on the determination of platinum with rhodamine 6G were examined; some interference was found from palladium and rhodium. Trace amounts of platinum in palladium could be determined after separation of platinum by extraction with triphenylphosphine oxide in 1,2-dichloroethane.