Determination of Ni(II), Cd(II) and Pb(II) ions by preconcentration on modified silica gel with pyromellitic dianhydride with flame atomic absorption spectrometry

In this thesis study, Ni(II), Cd(II) and Pb(II) ions at trace level were preconcentrated using pyromellitic dianhydride modified silica gel (PMDA-SG) and then determined by flame atomic absorption spectrometry. Characterization of PMDA-SG was performed by C, H, N elemental analysis and FT-IR spectroscopy. In the preconcentration studies with column solid phase extraction technique, the effects of factors such as solution pH, type and concentration of eluent solution, flow rate, solution volume, matrix ions were investigated. The optimum condition for the preconcentration of Ni(II), Cd(II) and Pb(II) ions in the PMDA-SG filled column as follows; the pH of the sample solution was 7.0, the sample flow rate was 5 mL/min, the maximum volume of the solution was 500 mL, and the eluent was 5 mL of 1,0 mol L-1 HNO3 solution. The recovery of Ni(II), Cd(II) and Pb(II) ions was quantitatively found even in the presence of matrix ions at levels that could be found in environmental samples. The accuracy of the developed method was demonstrated by analyzing standard reference material water samples. The precision of the method was evaluated by determination of Ni(II), Cd(II) and Pb(II) levels in the sample solution (50 mL) containing Ni(II), Cd(II) and Pb(II) ions at 20 ng mL-1 (n = 5). The quantitative recoveries and relative standard deviation values lower than 5% were obtained. The concentrations of Ni(II), Cd(II) and Pb(II) ions in water samples from tap water, Sapanca Lake, Çark Stream and Sakarya River were successfully determined by using the developed method.