Silica gel functionalized with resacetophenone: synthesis of a new chelating matrix and its application as metal ion collector for their flame atomic absorption spectrometric determination

Abstract

Silica gel modified with 3-aminopropyltriethoxysilane was anchored with resacetophenone to prepare a new chelating surface (or matrix). It was characterized with cross polarization magic angle spinning 13C NMR spectroscopy and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and used for the separation and preconcentration of Cu(II), Pb(II), Ni(II), Fe(III), Cd(II), Zn(II) and Co(II) prior to their determination by flame atomic absorption spectrometry (FAAS). The optimum pH ranges for quantitative sorption are 6.0–7.5, 5.5–7.5, 5.0–7.0, 6.5–7.5, 6.0–7.5, 6.0–7.0 and 6.0–7.5 for Cu, Pb, Fe, Zn, Co, Ni and Cd, respectively. All the metals can be desorbed with 3 mol dm −3 HCl or HNO 3. The sorption capacity for these metal ions is in range of 57.8–365.0 μmol g −1 of chelating matrix. Tolerance limits for electrolytes NaNO 3, NaCl, NaBr, Na 2SO 4 and Na 3PO 4 and cations Ca(II) and Mg(II) in the sorption of these metal ions are reported. Preconcentration factors of 200, 300, 150, 250, 250, 200 and 200 for Cd, Co, Zn, Cu, Pb, Fe and Ni, respectively, are obtained and t 1/2 values are <1 min except for Cd. 95% extraction by a batch method takes ≤25 min. The simultaneous enrichment and determination of all the metals are possible if the total load of the metal ions is less than the sorption capacity. In river water samples all these metal ions were enriched with the present matrix and determined with a flame atomic absorption spectrometer (R.S.D. ≤ 7.7%). Copper contents of pharmaceutical samples (vitamin capsule) were preconcentrated with the present chelating matrix and estimated with flame AAS, with R.S.D. ∼ 2.2%. The results are in the good agreement with the certified value, 0.4 mg/g of capsule.