title: Use of xylenol orange and cetylpyridinium chloride in rapid spectrophotometric determination of zinc in pharmaceutical products.
abstract: A simple, rapid, and sensitive spectrophotometric method for the determination of zinc(II) is performed, based on colour reaction between the metal ion and xylenol orange in the presence of surfactant cationic cetylpyridinium chloride. The important analytical parameters and their effects on the reported system are investigated. Zinc(II) reacts with the reagent and surfactant in the ratio 1:2:4 (metal:ligand:surfactant) in the pH range 5.0-6.0 to form a ternary complex with an absorption maximum at 580 nm. The reaction was extremely rapid, at room temperature, and the absorbance value remains unchanged for at least 168 h. The apparent stability constant of the complex was found to be K = 1.05 x 10(10), and the method adheres to Beer's law for 1-20 microg zinc(II) per 25 ml with apparent molar absorptivity of 1.1 x 10(4) l mol cm(-1). The effect of foreign ions was tested by taking a constant concentration of metal ion and determining its concentration in the presence of large number of foreign ions. The method was applied for determination of zinc(II) in dermal ointments where excellent agreement between reported and obtained results were achieved. The relative standard deviation was better than 2%.
authors.affiliation: Laboratory of Analytical Chemistry, Institute of Chemical Engineering, University of Bejaia, Algeria. mohamedbenamor@hotmail.com
authors.forename: M
authors.initials: M
authors.lastname: Benamor
authors.forename: K
authors.initials: K
authors.lastname: Belhamel
authors.forename: M T
authors.initials: MT
authors.lastname: Draa
mesh_terms: D002594:Cetylpyridinium; D002623:Chemistry Techniques, Analytical; D003124:Colorimetry; D003902:Detergents; D005456:Fluorescent Dyes; D007202:Indicators and Reagents; D009824:Ointments; D010636:Phenols; D012044:Regression Analysis; D013053:Spectrophotometry / Q000379:methods*; D013454:Sulfoxides; D014992:Xylenes; D015032:Zinc / Q000032:analysis* / Q000737:chemistry
chemical_list: D003902:Detergents; D005456:Fluorescent Dyes; D007202:Indicators and Reagents; D009824:Ointments; D010636:Phenols; D013454:Sulfoxides; D014992:Xylenes; D002594:Cetylpyridinium; D015032:Zinc; C016833:xylenol orange