Abstract
An extraction-spectrophotometric method for the determination of copper using 5-bromosalicylaldoxime (5-Br·SA) was studied and the result was applied to the analysis of aluminum alloys. Copper(II) reacts with 5-Br·SA to form a complex in aqueous solution in the pH range of 2.67.6, which can be extracted quantitatively into chloroform. The acid dissociation constants for 5-Br·SA were evaluated spectrophotometrically, and the optimum conditions for the determination of copper were confirmed. The copper complex in chloroform was stable and showed a maximum absorption at 356 nm with apparent molar absorption coefficient of 8.77×103 dm3 mol-1 cm-1. Conformity to Beer's law over the range of 032 μg of copper(II) in 10 ml of chloroform was obtained, with the sensitivity being 7.36×10-3 μg Cu (II) /cm2 for 0.001 absorbance unit. For 15 μg of copper (II), the coefficient of variation was 0.24% in 7 determinations. The recomended procedure is as follows: take an aliquot of sample solution containing up to 30 μg of copper (II) to a 50 ml separatory funnel. Add 1.5 ml of 2 M sodium perchlorate solution and 10 ml of phosphate buffer solution (pH=5.0), and dilute with water to about 30 ml. Then add 10 ml of 0.02M 5-Br· SA chloroform solution and shake vigorously for 10 min. Filter the organic phase through a dry filter paper and measure the absorbance at 356 nm against a reagent blank. By this method the copper (II) in the presence of 10 mg of aluminum (III) can be determined, although iron (III) and gold (III) seriously interfered with the determination of copper (II), the influence of iron (III) up to 1 mg could be eliminated by the addition of fluoride. Copper (II) in aluminum alloys can be determined accurately with a good reproducibility.
