Spectrophotometric determination of trace amounts of copper in steel, stainless steel and aluminium alloys with 2,2′-biquinolyl and tetrabromophenolphthalein ethyl ester

An extraction-spectrophotometric determination of copper with 2,2′-biquinolyl and tetrabromophenolphthalein ethyl ester (TBPE) is described. The copper-2,2′-biquinolyl complex in 1,2-dichloroethane forms a blue ion complex with TBPE in an aqueous layer buffered at pH 6.0. The molar absorptivity of the ion complex is 9.4 × 104 l mol–1 cm–1 at 610 nm. The concentrations of 2,2′-biquinolyl, TBPE, hydroxylammonium chloride and tartaric acid available for 0.1 µg ml–1 of copper are 5 × 10–4M, 8 × 10–4M, 1% and 1%, respectively. This method can be appl.ied to the determination of trace amounts of copper in steel, stainless steel and aluminium alloys.