Investigation of 3-amino-1,2,4-triazole azodye derivatives as reagents for determination of mercury(II)

The reaction of mercury(II) with 3-(2,4-dihydroxyphen-1-ylazo)-1,2,4-triazole (HL¹), 3-(2-hydroxy-5-methylphen-1-ylazo)-1,2,4-triazole (HL²), 3-(2-hydroxy-5-ethoxycarbonylphen-1-ylazo)-1,2,4-triazole (HL³), 3-(2-hydroxy-5-acetylphen-1-ylazo)-1,2,4-triazole (HL⁴), 3-(2-hydroxy-5-formylphen-1-ylazo)-1,2,4-triazole (HL⁵), and 3-(2-hydroxy-5-bromophen-1-ylazo)-1,2,4-triazole (HL⁶) was studied. A new, direct, and simple procedure was suggested for the spectrophotometric determination of mercury(II) based on its complexation reaction with HL¹-HL⁶. The best reagent was found to be HL³ due to its high sensitivity and selectivity. In aqueous media of pH 9.0 containing 40 vol. % of methanol, Hg(II) reacts with HL³ to form a 1:2 (Hg(II) · HL³) complex having a sensitive absorption peak at 490 nm with the molar extinction coefficient of 3.31 × 10⁴ L mol⁻¹ cm⁻¹ using 4 × 10⁻⁴ M of the reagent. Beer’s law is obeyed over the range from 0.00 μg mL⁻¹ to 12.04 μg mL⁻¹ of mercury(II). The proposed method was applied in the determination of mercury(II) in tap water, seawater and synthetic seawater samples, without the need of prior treatment, with satisfactory results.