Extraction-spectrophotometric determination of tantalum(V) with substituted N-arylhydroxamic acids

Abstract

An extraction-spectrophotometric method for the determination of microgram amounts of tantalum(V) based on the extraction of the tantalum-N-4-chlorophenyl-3,4,5-trimethoxycinnamohydroxamic acid (Ta-PTCHA) complex from HCI medium into toluene is described. Brilliant Green (BG) is added to the organic phase containing the binary complex and the absorbance of the ternary system is measured. The molar absorptivities of the Ta-PTCHA and Ta-PTCHA-BG complexes are 2.9 × 10⁴(λ_max. 385 nm) and 2.3 × 10⁴(λ_max. 635 nm) l mol^–1 cm^–1, respectively. The method has been applied to the determination of tantalum in the presence of niobium(V) and tantalum in standard samples.