Simultaneous Determination of Nickel and Cobalt in Chemical Plating Layers by Standard Additions-dual Wavelength Spectrophotometry

The simultaneous determination of cobalt and nickel in chemical plating layers via standard additions-dual wavelength spectrophotometry was studied, and the synthetic mixtures of cobalt and nickel and the actual plating samples were determined in this paper. In acetic acid-sodium acetate buffer solution at pH 3.8, determination wavelength and reference wavelength of simultaneous determination of cobalt and nickel by color reagent 5-Br-PADAP are equal to 564 nm and 592nm respectively. At the two wavelengths, Beer's law is obeyed in the concentration range of 0～50μg/25mL or 0～40μg/25mL for nickel respectively, but for cobalt both are 0～50μg/25ml. The method has been applied to the simultaneous determination of synthetic mixtures of cobalt and nickel and plating layers of the actual chemical Co-Ni-P and Ni-Co-P alloy plating with a satisfactory result and a recovery rate ranging from 95% to 105%.