Solvent extraction and spectrophotometric determination of lanthanides with N-phenylcinnamohydroxamic acid

Abstract

The solvent extraction and spectrophotometric determination of lanthanides with N-phenylcinnamohydroxamic acid (PCHA) is described. Lanthanum (III), praseodymium(III), neodymium(III), samarium(III), gadolinium(III), and terbium(III) form 1:3 yellow coloured binary complexes (λ_max 380 nm) with PCHA which are extractable quantitatively into chloroform, at <em>p</em>H 9.0<em>. </em>Sensitivity of the spectrophotometric determination is enhanced by the addition of xylenol orange to the organic extract having maximum absorbance between 590 and 610 nm. Efforts have been made to study the extraction equilibria by calculating the extraction constants and the two phase stability constants of the complexes. The possible separation of the lanthanides from each other has been studied by evaluating separation factor(s) and <em>p</em>H1/2 (<em>p</em>H of 50% extraction). The lanthanides are determined in standard United State Geological Samples (USGS) and IAEA Soil-5 samples.