Spectrophotometric determination of copper in sulfuric acid anodizing liquor with l-(2-pyridylazo)-2-naphthol

The color reaction conditions of Cu 2+ and l-(2-pyridylazo)-2-naphthol (PAN) were researched, and a new method was developed for the determination of copper in sulfuric acid anodizing liquor. It was based on the fact that copper forms a stable complex with PAN in acid solution with Triton X-100 as solubilizing and sensitizing agent and gelatin as protecting agent. The maximum absorption of the complex is 558 nm with apparent molar absorptivity of 2.25 × 10 4 L · mol -1 · cm -1. The linear range of the method is 0-3.2 μg/mL,and the detection limit is 0.028 μg/mL.The recoveries of copper in different levels were 97.2%-105.6% with RSD of no more than 0.34%. Moreover, no interference was found in the presence of other co-existing ions.