Synthesis, characterization and applications of pyrocatechol modified amberlite XAD-2 resin for preconcentration and determination of metal ions in water samples by flame atomic absorption spectrometry (FAAS)

A new chelating resin is prepared by coupling Amberlite XAD-2 with pyrocatechol through an azo spacer, characterized (by elemental analysis, IR and TGA) and studied for preconcentrating Cd(II), Co(II), Cu(II), Fe(III), Ni(II) and Zn(II) using flame atomic absorption spectrometry (FAAS) for metal monitoring. The sorption is quantitative in the pH range 3.0–6.5, whereas quantitative desorption occurs instantaneously with 2 M HCl or HNO3 The sorption capacity has been found to be in the range 0.023–0.092 mmol g−1 of resin. The loading half time (t1/2) is 1.4, 4.8, 1.6, 3.2, 2.3 and 1.8 min, respectively for Cd, Co, Cu, Fe, Ni and Zn. The tolerance limits of electrolytes NaCl, NaBr, NaNO3, Na2SO4 and Na3PO4 in the sorption of all the six metal ions (0.2 μg ml−1) are reported. The Mg(II) and Ca(II) are tolerable with each of them (0.2 μg ml−1) up to a concentration level of 0.01–1.0 M. The enrichment factor has been found to be 200 except for Fe and Cu for which the values are 80 and 100, respectively. The lowest concentration of metal ion for quantitative recovery is 5, 10, 20, 25, 10 and 10 μg l−1 for Cd, Co, Cu, Fe, Ni and Zn, respectively. The simultaneous determination of all these metal ions is possible and the method has been applied to determine all the six metal ions in tap and river water samples (RSD≤3.9 and 7.3%, respectively). The cobalt content of pharmaceutical vitamin tablets is estimated by FAAS (RSD∼2%) after its preconcentration with the present chelating resin.