Nonextractive Trace Level Simultaneous Determination of Mercury(II) and Zinc(II) in Environmental Samples with 2‐(5‐Bromo‐2‐pyridylazo)‐5‐diethylaminophenol and Cetylpyridinium Chloride

Abstract

A simple, rapid, selective, and sensitive method for the derivative spectrophotometric determination of Hg(II) and its simultaneous determination in the presence of Zn(II) using 2‐(5‐bromo‐2‐pyridylazo)‐5‐diethylaminophenol in the presence of cetylpyridinium chloride, a cationic surfactant, has been developed. The molar absorption coefficient and analytical sensitivity of the 1∶1 Hg(II) complex at 558 nm (λ_max) are 5.78×10⁴ L mol⁻¹ cm⁻¹ and 0.67 ng mL⁻¹, respectively. The detection limit of Hg(II) is 1.40×10⁻² ng mL⁻¹, and Beer's law is valid in the concentration range 0.05–2.40 µg mL⁻¹. Overlapping spectral profiles of Hg(II) and Zn(II) complexes in zero‐order mode interfere in their simultaneous determination. However, 0.10–2.00 µg mL⁻¹ of Hg(II) and 0.065–0.650 µg mL⁻¹ of Zn(II), when present together, can be simultaneously determined at zero cross point of the derivative spectrum, without any prior separation. The relative standard deviation for six replicate measurements of solutions containing 0.134 µg mL⁻¹ of Hg(II) and 0.620 µg mL⁻¹ of Zn(II) is 1.72 and 1.47%, respectively. The proposed method has successfully been evaluated for trace level simultaneous determination of Hg(II) and Zn(II) in environmental samples.

Keywords:

• 5‐Br‐PADAP
• simultaneous determination
• environmental samples
• zero crossover point

Acknowledgments

The authors gratefully acknowledge the financial assistance provided by UGC to S.R. and to Prof. H. B. Singh for suggestions.