SIMULTANEOUS SPECTROPHOTOMETRIC DETERMINATION OF ZINC(II) AND NICKEL(II) WITH 1-(2-PYRIDYLAZO)-2-NAPHTHOL

A new procedure for the simultaneous spectrophotometric determination of Zn(II) and Ni(II) with 1-(2-pyridylazo)-2-naphthol as chromogenic reagent has been developed. It is based on resolution of the mixed spectrum over the wavelength range 530-590 nm by applying a least-squares fitting program to standard spectra from each component. The spectra are recorded at an apparent pH of 5.0, provided by an acetate buffer in a mixed 60: 40 v/v 2-ethoxyethanol/water medium. The relative standard deviations for determination of 13.7-mu-g of Ni and 31.0-mu-g of Zn were 1.9 and 1.0%, respectively (8 replications). The method has been applied to the analysis of iron surfaces coated with a Zn-Ni alloy. The results are compared with those obtained by atomic-absorption spectrophotometry.