Validated uv-vis spectrophotometric method for the determination of copper using 2,3,4,6/-tetrahydroxy-3/-sulfoazobenzene in real samples

A selective and sensitive spectrophotometric method has been proposed for the determination of copper by forming red-brown chelate at pH 3.5 (3-4) with 2,3,4,6/-tetrahydroxy-3/-sulfoazobenzene (THSA). Molar absorptivity of the complex having metal ligand ratio of 1:2 is 4.03 × 104 L mol-1 cm-1 at 485 nm. Its conditional stability constant (log K) is 7.98. The developed method obeys Beer's law for 0.032–1.905 µg mL-1 Cu(II). Group 1A elements, group 2A elements, rare earth elements, group 7A elements, phosphates, ascorbic acid and cations do not interfere copper determination. The proposed method is rapid and simple, and it can be easily applied on certificated alloys and pharmaceutical formulations for determining copper. (author)