Analytical Sciences

Simultaneous Derivative Spectrophotometric Determination of Zinc and Cadmium with 2-(5-Bromo-2-pyridylazo)-5-diethylaminophenol in the Presence of Cetylpyridinium Chloride

Narinder K. AGNIHOTRI, Sonia RATNANI, Vinay K. SINGH, and Har B. SINGH

Department of Chemistry, University of Delhi, Delhi 110007, India

A selective and sensitive derivative photometric method has been developed for the determination of trace amounts of Zn²⁺ with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol in the presence of cetylpyridinium chloride, a cationic surfactant. The molar-absorption coefficient and analytical sensitivity of the 1:2 complex at 554 nm are 1.19 × 10⁵ L mol^-1 cm^-1 and 0.56 ng mL^-1, respectively. The detection limit is 1.96 × 10^-2 ng mL^-1 and Beer’s law is valid in the 0.02 - 0.66 µg mL^-1 range of Zn²⁺. The developed derivative procedure, using the zero-crossing measurement approach, is applied for the rapid and selective simultaneous determination of Zn²⁺ and Cd²⁺ in the range of 0.06 - 0.66 and 0.20 - 1.60 µg mL^-1, respectively. Complex matrices, including reference materials, environmental and biological samples and synthetic mixtures, have been successfully analyzed for trace amounts of the two metal ions.

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