Determination of lead at nanogram level in water samples by resonance light scattering technique using tetrabutyl ammonium bromide as a molecular probe

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