Abstract
A novel method of chemistry applicable to the determination of trace lead in water samples based on the resonance light scattering (RLS) technique has been developed. In dilute phosphoric acid medium, in the presence of a large excess of I-, Pb(II) can form [PbI4]2-, which further reacts with tetrabutyl ammonium bromide (TBAB) to form an ion-association compound. This results in significant enhancement of RLS intensity and the appearance of the corresponding RLS spectral characteristics. The maximum scattering peak of the system exists at 402 nm. Under optimum conditions, there is a linear relationship between the relative intensity of RLS and concentration of Pb(II) in the range of 0.04–1.8 μg/mL for the system with a low detection limit of 0.74 ng/mL for Pb(II). Based on this fact, a simple, rapid, and sensitive method has been developed for the determination of Pb(II) at nanogram level by RLS technique using a common spectrofluorimeter. This analytical system was successfully applied to determining trace amounts of Pb(II) in water samples that agree well with the results by atomic absorbance spectrometry (AAS). KEY WORDS: Lead, Tetrabutyl ammonium bromide (TBAB), Potassium iodide (KI), Resonance light scattering (RLS) Bull. Chem. Soc. Ethiop. 2012, 26(1), 1-8.DOI: http://dx.doi.org/10.4314/bcse.v26i1.1
Highlights
As is well known, heavy metal pollution has been a focus of attention all over the world
[PbI4]2- + 2TBAB+ → [PbI4][tetrabutyl ammonium bromide (TBAB)]2 According to the following formula of resonance light scattering (RLS) [27, 28]
32π 3V 2n2 N 3λ04 δn 2 + δk 2 where n is the refractive index of the medium, N is the molarity of the solution, λ0 is the wavelength of the incident and scattered light, V2 is the square of molecular volume, δn and δk are the fluctuations in the real and imaginary components of the refractive index of the particle, respectively
Summary
Heavy metal pollution has been a focus of attention all over the world. Metal ions frequently contained in industrial and municipal wastewater can be harmful to aquatic life and animal health. Due to accumulative toxicity to the human body, lead is one of the most toxic metals to man. There are high levels of Pb(II) in wastewater from manufacturing of storage battery, drainage from lead ore mines, paints, munitions, and petroleum refining. Many methods have been used to determine the content of this toxic heavy metal. They have some disadvantages relative sensitivity, selectivity, stability and operation. It is an urgent need to develop a simple and sensitive conventional method for measuring lead ion in water samples
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