Spectrophotometric investigation of the complexation equilibria of zirconium(IV) withlawsone and determination of zirconiumSpektrophotometrische Untersuchung der Komplexierungsgleichgewichte von Zirkonium(IV) mitLawsone und Bestimmung von Zirkonium

The complexation equilibria of zirconium(IV) withlawsone (2-hydroxy-1,4-naphthoquinone) have been studied spectrophotometrically in 40% (v/v) ethanol at 20°C and at an ionic strength of 0.1M (NaClO4). A complete picture of the solution equilibria in thepH range 1.5–4.0 is presented. The absorbance vs.pH graphs were analyzed to characterize the complexation equilibria in solution. A simple, rapid, selective, and sensitive method for the spectrophotometric determination of zirconium is proposed based on the formation of Zr(lawsone)2 atpH 3.3(λmax=450 nm, ε=1.13×104l · mol−1 · cm−1). The interference caused by a number of ions can be masked by the addition of cyanide. The method has been applied to the determination of zirconium in some synthetic samples.