EXTRACTIVE SPECTROPHOTOMETRIC DETERMINATION OF NIOBIUM(V) USING 3-HYDROXYFLAVONE

A simple, rapid method for the spectrophotometric determination of niobium in trace amounts is presented, employing 3-hydroxyflavone as a ligand for the complexation of the metal ion and extracting the coloured complex into chloroform from 4M HClO4 solution. Beer's law is obeyed in the range 0.0 to 3.2 mug ml-1 Nb(V), with a lower working limit of 0.1 mug ml-1 Nb(V). Molar absorptivity and Sandell's sensitivity of the complex at 395 nm are 4.088 x 10(4)l mol-1 cm-1 and 0.002 mug Nb(V) cm-2, respectively. The stoichiometry of the complex is established as 1:2 by Job's and mole ratio methods. The method is free from the interference of a large number of analytically important elements. The proposed system handles satisfactorily the analysis of several samples of varying complexity. The results are highly reproducible with a relative standard deviation of 0.34% for 20 mug of Nb.