title: Spectrophotometric studies on the complexation equilibria of Ni and Pb with 2-carboxy-2-hydroxy-5'-sulfo-formazylbenzene. Simultaneous determination of trace amounts of Ni and Pb.
abstract: Spectrophotometric studies have been made to investigate the reaction of Nickel and Lead with 2-carboxy-2'-hydroxy-5'-sulfoformazyl-benzene (zincon) in 50%(v/v) ethanol-water at 25 degrees C and an ionic strength of 0.1 M NaClO4. A complete picture of the complexation equilibria in the pH range (4.2-12.0) for nickel and (1.9-11.5) for lead are presented. Simple, rapid, selective and sensitive methods for the spectro-photometric determination of nickel and lead has been developed based on the color reaction of their complexes with zincon. The methods allow the determination of 4.69 microg mL(-1) of nickel at pH = 6.3 (lambdamax = 665 nm) and 10.3 microg ml(-1) of lead at pH = 5.6 (lambdamax = 610 nm). The apparent molar absorptivities were epsilon = 1.3 x 10(4) L mol(-1) cm(-1) for nickel and epsilon = 0.6 x 10(4) L mol(-1) cm(-1) for lead. The interference of a large number of foreign ions and complexing agents has been studied. Thiosulphate, as masking agent allows the simultaneous determination of nickel and lead in the presence of high concentrations of copper. Ascorbic acid, sodium cyanide and or sodium fluoride provide the elimination of many other interferences. The methods have been applied successfully to the simultaneous determination of nickel and lead in an aluminium and non-ferrous alloy.
authors.affiliation: Chemistry Department, Faculty of Science, Assiut University, Assiut, Egypt. elham_hashem@yahoo.com
authors.forename: Elham Y
authors.initials: EY
authors.lastname: Hashem
authors.forename: Mohamed S
authors.initials: MS
authors.lastname: Abu-Bakr
authors.forename: Sawsan M
authors.initials: SM
authors.lastname: Hussain
mesh_terms: D000497:Alloys / Q000737:chemistry; D001391:Azo Compounds / Q000737:chemistry*; D005562:Formazans; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents / Q000737:chemistry; D007700:Kinetics; D007854:Lead / Q000032:analysis / Q000737:chemistry*; D009532:Nickel / Q000032:analysis / Q000737:chemistry*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013056:Spectrophotometry, Ultraviolet / Q000379:methods
chemical_list: D000497:Alloys; D001391:Azo Compounds; D005562:Formazans; D007202:Indicators and Reagents; D007854:Lead; C009809:2-carboxy-2'-hydroxy-5'-sulfoformazylbenzene; D009532:Nickel