Spectrophotometric Determination of Niobium with Hydrogen Peroxide and 2-(5-Bromo-2-pyridylazo)-5-diethylaminophenol in Steel and Apatite after Its Extractive Separation as α-benzoin Oxamate

Abstract

A sensitive method for the spectrophotometric determination of niobium(V) based on the formation of its complex with 2-(5-Bromo-2-pyridylazo)-5-diethylaminophenol in the presence of hydrogen peroxide has been developed. The molar absorptivity at 591nm is 7.43×10⁴l mol^-1 cm^-1 at pH 4.0±1.0. This method becomes selective for niobium(V) after a preliminary extraction of its complex with α-benzoin oxime from 5-9M hydrochloric acid, thus permitting the determination of traces of niobium in the presence of a large amount of other ions. It has been applied to the determination of niobium in materials of certified Nb content: steel and apatite samples.