Solid phase extraction of lead (II), copper (II), cadmium (II) and nickel (II) using gallic acid-modified silica gel prior to determination by flame atomic absorption spectrometry

The immobilization of gallic acid on the surface of amino group-containing silica gel phases for the formation of a newly chelating matrix (GASG) is described. The newly synthesized extractant, characterized by the diffuse reflectance infrared Fourier transformation spectroscopy and elemental analysis, was used to preconcentrate Pb(II), Cu(II), Cd(II) and Ni(II). The pH ranges for quantitative sorption and the concentrations of HCl for eluting Pb(II), Cd(II), Cu(II) and Ni(II) were opimized, respectively. The sorption capacity of the matrix has been found to be 12.63, 6.09, 15.38, 4.62 mg/g for Pb(II), Cd(II), Cu(II) and Ni(II), respectively, with the preconcentration factor of ∼200 (∼100 for Cd(II)). The effects of flow rates, the eluants, the electrolytes and cations on the metal ions extraction, as well as the chelating matrix stability and reusability, were also studied. The extraction behavior of the matrix was conformed with Langmuir's equation. The present preconcentration and determination method was successfully applied to the analysis of synthetic metal mixture solution and river water samples. The 3σ detection limit and 10σ quantification limit for Pb(II), Cu(II), Cd(II) and Ni(II) were found to be 0.58, 0.86, 0.65, 0.92 μg/L and 1.08, 1.23, 0.87, 1.26 μg/L, respectively.