Sensitized extraction spectrophotometric determination of Hg(II) with dithizone after its flotation as ion-associate using iodide and ferroin

This paper describes a simple and highly selective method for the separation, preconcentration and spectrophotometric determination of extremely low concentration of mercury. The method is based on the flotation of an ion-associate of HgI42− and ferroin between aqueous and n-heptane interface at pH 5. The ion-associate was then separated and treated with ammonia and dithizone solutions to extract only the mercury chelate with CH2Cl2. The measurement is feasible when the volume of the water sample containing Hg(II) was varied over 50-800 ml. Beer's law was obeyed over the concentration range of 8 × 10−9 to 1.6 × 10−7 mol l−1 with an apparent molar absorptivity of 6.53 × 106 l mol−1 cm−1 for a 500 ml aliquot of the water sample. The detection limit (n = 7) was 5.0 × 10−10 mol l−1 and the R.S.D. (n = 5) for 8.0 × 10−7 mol l−1 of Hg(II) was 3.7%. A notable advantage of the method is that the determination of Hg(II) is free from the interference of almost all cations and anions found in the environmental and waste water samples. The determination of Hg(II) in tap, synthetic sea water and human hair samples was carried out by the present method and cold vapor atomic absorption spectrometry (CV-AAS). The results were satisfactorily comparable so that the applicability of the proposed method was confirmed to the real samples.