Silica Gel Coated with Schiff's Base: Synthesis and Application as an Adsorbent for Cadmium, Copper, Zinc, and Nickel Determination after Preconcentration by Flame Atomic Absorption Spectrometry

A method for the preconcentration of Cd(II), Cu(II), Zn(II), and Ni(II) is proposed using a minicolumn filled with silica gel modified by Schiff's base. The retained analytes on the ligand-coated silica gel were recovered with a small volume of HNO₃ (nitric acid). The metal ions in the eluent were determined by flame atomic absorption spectrometer (FAAS). Different factors, including the pH of the sample solution, the sample volume, the amount of silica gel, eluent volume and matrix effects for preconcentration were examined. The recoveries for the analytes under optimum working conditions were higher than 95%. The relative standard deviations of the determination were 1.50, 2.10, 2.40, 3.43% for Cu(II), Cd(II), Zn(II) and Ni(II). The limits of detection (3s, n = 10) for Cd(II), Cu(II), Zn(II), and Ni(II) were found to be 3, 5, 5 and 4.7 ngL^–1. The proposed method was applied to the analysis of some natural water samples and standard reference aluminum alloy material (NBS SRM 85b).