• Shraddha Y. Birpan
• Dr. Pranjali Shinde

A simple, sensitive and validated UV–Visible spectrophotometric method was developed for the simultaneous determination of Cu(II), Ni(II) and Co(II) using a hydroxytriazene reagent as a chromogenic chelating agent. The analytical procedure was optimized by systematically investigating the effects of experimental variables, including pH, buffer composition, reagent concentration, reaction time and temperature. The metal–hydroxytriazene complexes exhibited intense absorption maxima at 545, 470 and 590 nm for Cu(II), Ni(II) and Co(II), respectively, while the free reagent showed an absorption maximum at 365 nm. The pronounced bathochromic shifts observed upon complex formation confirmed the formation of coloured metal–ligand complexes and provided well-separated analytical wavelengths suitable for simultaneous determination. An acetate–acetic acid buffer at pH 6.5 was selected as the optimum reaction medium, with 3.0 mL of 0.1% hydroxytriazene reagent and a reaction time of 15 min. The optimum temperature for colour development was found to be approximately 25–30 °C, and therefore the analytical measurements were performed at room temperature (25 ± 2 °C). The proposed method obeyed Beer’s law in the concentration ranges of 0.2–1.6 µg mL⁻¹ for Cu(II) and Ni(II), and 0.3–1.8 µg mL⁻¹ for Co(II), with correlation coefficients of 0.9998, 0.9997 and 0.9995, respectively. The molar absorptivities were 1.86 × 10⁴, 1.42 × 10⁴ and 1.65 × 10⁴ L mol⁻¹ cm⁻¹ for Cu(II), Ni(II) and Co(II), respectively. Sandell’s sensitivities were found to be 0.0034, 0.0041 and 0.0036 µg cm⁻² for Cu(II), Ni(II) and Co(II), respectively. The limits of detection were 0.018, 0.024 and 0.021 µg mL⁻¹, while the corresponding limits of quantification were 0.054, 0.072 and 0.063 µg mL⁻¹. Accuracy studies for Cu(II) gave recoveries of 99.6–100.5% with relative standard deviations below 1%, whereas intra-day and inter-day precision studies showed RSD values below 1.5%. The method also exhibited satisfactory robustness and ruggedness under small deliberate variations in experimental conditions. The proposed procedure was successfully applied to synthetic mixtures and real samples, including natural water, industrial effluent, pharmaceutical and alloy samples. The results demonstrate that the hydroxytriazene-based method provides a convenient, sensitive, precise and economical approach for the simultaneous spectrophotometric determination of Cu(II), Ni(II) and Co(II).

Hydroxytriazene; Cu(II); Ni(II); Co(II); UV–Visible spectrophotometry; Chromogenic reagent; Metal–ligand complex; Simultaneous determination; Trace metal analysis; Method validation.

"A Sensitive and Validated Hydroxytriazene-Based UV–Visible Spectrophotometric Method for Simultaneous Determination of Cu(II), Ni(II) and Co(II)", International Journal of Emerging Technologies and Innovative Research (www.jetir.org), ISSN:2349-5162, Vol.13, Issue 9, page no.d453-d459, September-2026, Available :http://www.jetir.org/papers/JETIR2609343.pdf

"A Sensitive and Validated Hydroxytriazene-Based UV–Visible Spectrophotometric Method for Simultaneous Determination of Cu(II), Ni(II) and Co(II)", International Journal of Emerging Technologies and Innovative Research (www.jetir.org | UGC and issn Approved), ISSN:2349-5162, Vol.13, Issue 9, page no. ppd453-d459, September-2026, Available at : http://www.jetir.org/papers/JETIR2609343.pdf