Pyrogallol immobilized amberlite XAD-2: A newly designed collector for enrichment of metal ions prior to their determination by flame atomic absorption spectrometry

Pyrogallol is covalently linked with the benzene ring of Amberlite XAD-2, through an azo (-N=N-) spacer group and the resulting new polymer characterized by elemental analyses, thermogravimetric analysis (TGA) and infrared (IR) spectra. It has been used for separation and preconcentration of Cu(II), Cd(II), Co(II), Ni(II), Pb(II), Zn(II), Mn(II), Fe(III) and U(VI) prior to their determination by flame atomic absorption spectrometry (FAAS) or fluorimetry (for U(VI) only). The pH ranges for quantitative sorption are 5.5-6.5, 5.5-7.5, 5.5-7.0, 5.5-7.0, 5.5-6.5, 5.5-6.5, 5.5-8.0, 5.5-6.2 and 5.5-6.2, respectively, for the nine metal ions, which can be desorbed (recovery 90-99%) with 4 mol L-1 HNO3 or HCl. The sorption capacity of the resin has been found to be in the range 4.10 to 6.71 mg of metal g(-1) of dry resin. The loading half time (t(1/2)) was less than or equal to3.3 min for all the metal ions. The effects of NaF, NaCl, NaNO3, Na2SO4, and Na3PO4 on the sorption of these metal ions (0.2 mug mL(-1)) are reported. The Ca(II) and M-(II) are tolerable up to a concentration level of 40-400 and 25-240 mug mL(-1), respectively. The enrichment factor for Cu(II), Cd(II), Co(II), Ni(II), Pb(II), Zn(II), Mn(II), Fe(III) and U(VI) has been found to be 65, 40, 65, 120, 25, 160, 120, 140, and 70 (concentration level 2-25 ng mL(-1)), respectively. The limit of detection for these nine metal ions is 5.0, 1.3, 5.0, 4.0, 25.0, 0.5, 1.0, 2.0 and 1.0 ng mL(-1), respectively. After enrichment on the present matrix, the flame AAS method has been applied to determine these metal ions (except U) in river water samples (RSD less than or equal to 7%) and well water (RSD less than or equal to 8%). Uranium present in well water samples has been enriched on the present matrix and determined by a fluorimetric method (RSD less than or equal to 6%). The cobalt present in pharmaceutical vitamin tablets was also preconcentrated with the aid of the present chelating resin and determined by FAAS to be 1.93 mug g(-1) (RSD similar to4%).