Determination of Total Mercury in Soils, Waste Water and Sewage Effluents

Abstract

The cationic mercury(II)-1,10-phenanthroline binary chelate reacts with the acidic dye Thymol Blue (TB), in the pH range 5.2–7.0, to form an ion-pair extractable into chloroform. The effect of primary ligand and counter ion concentrations, pH, extraction solvent, extractability, standing time and co-existing ions has been thoroughly investigated. The molar absorptivity of the ion-pair, in chloroform, is 1.27×10⁵ l.mol⁻¹.cm⁻¹ at 420 nm. The calibration graph is rectilinear for 0.09–1.72 μg ml⁻¹ of mercury. The sensitivity index of the method is 0.0002 μg Hg.cm^2– and the detection limit is 0.018 μg ml⁻¹ of mercury. The stoichiometry of the extracted ion-pair is 1:2:1 (Hg-Phen-TB). The developed method has been successfully used to determine total mercury in soils, waste water and sewage effluents.

Key Words:

• Mercury
• determination
• spectrophotometry
• soil
• waste water
• sewage effluents
• 1,10-Phenanthroline
• Thymol Blue