Flow-Injection Study and Analytical Applications of the Reactions of Palladium(II) and Platinum(IV) with Tin(II) Chloride in Hydrochloric Acid Solutions

The interaction of palladium(II) and platinum(II) with tin(II) chloride in hydrochloric acid solutions was studied by flow-injection (FI) spectrophotometry. It was found using kinetic measurements in the stopped flow mode that the composition of detected products and the rate of their formation depend on the concentrations of tin(II) and chloride ions in the reaction zone and on the acidity of the solution. Optimal FI conditions were found, and the selectivity of interaction of palladium(II) with tin(II) chloride was estimated for the detection of the signal at 407 nm (yellow form) and 646 nm (green form). It was demonstrated that the reaction of the formation of yellow platinum(IV) complexes is slower than that for palladium(II), especially at rather low concentrations of hydrochloric acid in the reaction flow. Based on the detection of green complexes of palladium(II) with tin(II) chloride, a flow injection method was proposed for the selective spectrophotometric determination of palladium(II) in the presence of other platinum-group metals. The height of the recorded peak is directly proportional to the concentration of palladium(II) in the injected solution in the range of 0.028–0.300 mM. The method was used for the analysis of pharmaceuticals and industrial catalysts.