Spectrophotometric Determination of Lead by Extraction of the Mixed-Metal Complex Pb(II)-Ca-Purpurin (1,2,4-Trihydroxyanthraquinone)

Abstract

Mixtures of Lead(II) and Ca(II) form with purpurin (P; 1,2,4-Trihydroxyanthraquinone) the mixed-metal-complex PbCaP₃, which is extracted with isobutyl methyl ketone (IBMK) at pH 7.8. The molar absorptivity of the complex is 2.8 × 10⁴ l.mol^?1.cm^?1 at 575 nm and its conditional extraction constant 2.5 × 10¹⁷ 1⁴.mole^?4. The use of this complex for the spectrophotometric determination of lead up to 40 μg has been investigated. The proposed procedure has been successfully applied to the analysis of this metal in different samples.