title: Complexation equilibria and spectrophotometric determination of thorium(IV) with Lawsone.
abstract: The complex equilibria of Th4+ with Lawsone (2-hydroxy-1,4-naphthoquinone, LAS) were studied spectrophotometrically in 40% (v/v) ethanol water at 25 degrees C and an ionic strength of 0.1 M (NaClO4). The absorbance graphs were analysed to demonstrate and characterize the complex forming equilibria. A simple, rapid, selective and sensitive method for the spectrophotometric determination of trace amounts of thorium(IV) is developed. The complex formed at pH 2.1-3.6 (epsilon = 0.27 x 10(4) cm2 mol-1, at lambda = 440 nm) allows the determination of 5.8-32 micrograms/ml thorium. The effect of interferences was studied.
authors.affiliation: Chemistry Deprtment, Faculty of Science, Assiut University, Assiut, Egypt. elnady@yahoo.com
authors.forename: A B
authors.initials: AB
authors.lastname: al-Nady
authors.forename: Y
authors.initials: Y
authors.lastname: al-Shaibi
authors.forename: A
authors.initials: A
authors.lastname: Ba-Issa
authors.forename: W
authors.initials: W
authors.lastname: Ariqui
mesh_terms: D000042:Absorption; D004396:Coloring Agents / Q000737:chemistry*; D009285:Naphthoquinones / Q000737:chemistry*; D013053:Spectrophotometry / Q000379:methods; D013910:Thorium / Q000032:analysis / Q000737:chemistry*
chemical_list: D004396:Coloring Agents; D009285:Naphthoquinones; D013910:Thorium; C005090:lawsone