Spectrophotometric determination of mercury with 5,10,15,20-tetrakis(3-chloro-4-sulfophenyl)porphine by flow injection analysis

Abstract

5,10,15,20-tetrakis(3-chloro-4-sulfophenyl)porphine (m-Cl-TPPS₄) was synthesized and used for the Spectrophotometric determination of mercury by flow injection analysis. A pseudo-first-order reaction kinetic mechanism was proposed with a rate constant of 0.8 min⁻¹ for Hg(II) withm-Cl-TPPS₄ in the presence of 8-hydroxyquinoline in a medium of 1.0M acetic acid and sodium acetate buffer solution (pH 6.22). In the optimum conditions of reaction temperature (85 ° C), stopped-flow time (60 s) and sampling volume (100 μl), the method's relative standard deviation was 0.82% (n = 12) at 5.0 μg ml⁻¹ mercury, with a linear range of 0–12.0 μg ml⁻¹ and an analytical frequency of 60h⁻¹. The detection limit (3σ) was 0.025 μg ml⁻¹. Interference studies showed that most metal ions co-existing with Hg²⁺ could be tolerated at 100-fold excess levels, but Zn²⁺, Cu²⁺ and Mn²⁺ needed to be masked. The method has been applied to the analysis of water samples with satisfactory results.