Extraction and spectrophotometric determination of trace amounts of niobium with diphenylglioxal-bis-(2-hydroxybenzoylhydrazone)

A method is described for the direct spectrophotometric determination of microamounts of niobium based on its extraction into chloroform with dephenylglyoxal-bis-(2-hydroxy benzoyl) hydrazone (BSHB). This reagent builds up a chelate with Nb(V) in very acidic media, its chloroform solution being pink to reddish depending on niobium concentration (λ_max = 495 nm). Optimum conditions for chelate extraction and niobium determination have been established. The precision of procedure proposed, expressed in terms of relative standard deviation, is ±1.0%.It is shown that the method is sensitive, the molar absorptivity being 1.95 ± 0.02 × 10⁴ liter · mol⁻¹ · cm⁻¹ in the organic phase, and the interferences study demonstrates a high selectivity against common cations and the majority of those accompanying niobium in its natural sources and special alloys.