Micelle mediated selective extraction of lead after its complexation with thionine in aqueous samples prior to FAAS determination

A micelle mediated phase separation and preconcentration process of trace level Pb (II) ions in water samples, after chelating with thionine for determination by flame atomic absorption spectrometry (FAAS) was developed. The preconcentration step was based on the cloud point extraction of lead-thionine chelates with the non-ionic surfactant Tergitol NP-7 (TNP-7). Pb (II) ions were selectively reacted with thionine at pH 6 forming stable hydrophobic metal-chelates. The selectivity of the method proved in the presence of five different possible chelatable metal ions with thionine ligand. The parameters of the method were optimized for solution pH, surfactant concentration, ligand concentration, reaction temperature, incubation time and matrix ions. The reliability of the method was tested by relative standard deviation (RSD %), which was found to be less than 5%. The LOD and LOQ values were found as 1.5 and 5 mu g L-1 and the preconcentration factor was 25. The performance of the process was tested by standard reference material and analyte addition into the real samples.

Automated summary

A micelle mediated phase separation and preconcentration process was developed for the determination of trace level Pb (II) ions in water samples using flame atomic absorption spectrometry (FAAS) after chelation with thionine. The selectivity of the method was validated in the presence of five different possible chelatable metal ions with thionine ligand. The parameters of the method, including pH, surfactant concentration, ligand concentration, reaction temperature, incubation time and matrix ions, were optimized. The method showed good reliability with a relative standard deviation (RSD %) of less than 5% and had a detection limit (LOD) and quantitation limit (LOQ) of 1.5 and 5 μg/L, respectively.