Simultaneous determination of zinc and copper(II) with 1-(2-pyridylazo)2-naphthol in micellar media by spectrophotometric H-point standard addition method

The H-point standard addition method (HPSAM) was applied to handling spectrophotometric data for simultaneous determination of Zn²⁺ and Cu²⁺ or selective determination of Zn²⁺ in the presence of Cu²⁺. The ligand 1-(2-pyridylazo)2-naphthol (PAN) and its metal complexes (Zn-PAN and Cu(II)-PAN) were made water-soluble by the neutral surfactant Triton X-100, and therefore, no extraction with organic solvents was required. The method is based on the difference in absorbance of formed complexes between Zn²⁺ and PAN, at two different wavelengths at pH = 9.2. The formation of both the complexes was complete within five minutes. Zn²⁺ can be determined in the range of 0.2–25 μg/mL with satisfactory accuracy and precision in the presence of excess of Cu²⁺ and most other metal ions. Interference effects of common anions and cations were studied. Under working conditions, the proposed method was successfully applied to the simultaneous determination of Zn²⁺ and Cu²⁺ in several real and synthetic mixtures with different concentration ratio of Zn²⁺ and Cu²⁺. The text was submitted by the authors in English.