Determination of Trace Amounts of Lead Using the Flotation-spectrophotometric method

The present study describes a simple and highly selective method for separation, preconcentration and spectrophotometric determination of extremely low concentrations of lead. It is based on flotation of a complex of Pb²⁺ ions and Alizarin yellow between aqueous and n-hexane interface at pH = 6. The proposed procedure is also applied for determination of lead in both tap water and prepared sea water samples. Beer's Law was obeyed over the concentration range of 3.86 × 10^-8 To 8.20 × 10^-7 molL^-1 (8-170 ngmL^-1) with an apparent molar absorptivity of 1.33 × 10⁶ molL^-1 cm^-1 for a 100 mL aliquot of the water sample. The detection limit (n = 10) was 8.7 × 10^-9 molL^-1 (1.0 ngmL^-1) and the Relative standard deviation (R.S.D), (n = 10) for 7.2 × 10^-7 molL^-1 (150 ngmL^-1) of Pb (II) was 4.36%. A notable advantage of the method is that the determination of Pb (II) is free from the interference of almost all cations and ions found in the environment and waste water samples. The determination of Pb (II) in tap and synthetic seawater samples was also carried out by the present method. The results were satisfactorily comparable so that the applicability of the proposed method was confirmed to the real samples.