Separation and determination of microgram amounts of lanthanum(III) using N-phenylbenzohydroxamic acid and xylenol orange

Abstract

A simple solvent extraction and spectrophotometric method is described for the determination of microgram amounts of lanthanum(III) at pH 8.8–9.5 using N-phenylbenzohydroxamic acid and xylenol orange. The mixed ligand complex of lanthanum absorbs at 600 nm with a molar absorptivity of 6.5 × 10⁴| mol^–1 cm^–1. The system obeys Beer's law between 0.10 and 4.28 µg ml^–1 of lanthanum. The effect of pH, reagent and xylenol orange concentration, shaking time, stability of the complex, foreign ions and the stoicheiometry of the complex are discussed. Lanthanum has been determined in the presence of scandium, yttrium, cerium, praseodymium and neodymium and the method has been applied to the determination of lanthanum in standard samples.