Highly sensitive spectrophotometric determination of trace amounts of uranium(VI) with the thiocyanate–basic triphenylmethane dyes–gum arabic system

Abstract

Two highly sensitive spectrophotometric methods for the determination of trace amounts of uranium(VI) have been developed, based on its colour reactions with thiocyanate and triphenylmethane dyes (TPMD) in aqueous solution in the presence of gum arabic. Uranium(VI) reacts with thiocyanate and TPMD to form ion association complexes of composition (TPMD)₂[UO₂(SCN)₄]. The molar absorptivities are between 0.81 × 10⁵ and 5.71 × 10⁵ dm³ mol^–1 cm^–1, the highest value being found with Crystal Violet. Suitable conditions for the reactions, the effects of foreign ions and a pre-concentration procedure for uranium(VI) were investigated. The methods can be applied to the spectrophotometric determination of trace amounts of uranium(VI) in water and some ores.