Spectrophotometric investigation of palladium(II)-2-thiobarbituric acid complexes in aqueous and aqueous ethanolic media

Abstract

Palladium(II) forms 2:3 and 1:3 complexes with 2-thiobarbituric acid in water and in 30%V/V ethanol, respectively. The molar composition of the complexes has been determined by continuous variation and molar-ratio methods and confirmed by elemental analysis. The system conforms to Beer's law up to 10 µg ml^–1 of palladium [molar absorptivity (ε), 1.0 × 10⁴ l mol^–1 cm^–1 at 374 nm] in water and up to to 6 µg ml^–1(ε, 7.5 × 10³ l mol^–1 cm^–1 at 386 nm) in 30%V/V ethanol; the detection limits are 0.13 and 0.18 µg ml^–1 and the relevant Sandell's sensitivities are 0.0106 and 0.0141 µg cm^–2 per 0.001 absorbance unit, respectively.

Infrared spectroscopy has been used in order to establish the type of coordination between 2-thiobarbituric acid and palladium.

The tolerance limits for platinum metals and other cations are given. The experimental results have been critically analysed and a comparison with the main, most recent, spectrophotometric reagents for palladium is presented.