Cellulose based macromolecular chelator having pyrocatechol as an anchored ligand: synthesis and applications as metal extractant prior to their determination by flame atomic absorption spectrometry

Pyrocatechol is immobilized on cellulose via -NH-CH2-CH2-NH-SO2-C6H4-N=N- linker and the resulting macromolecular chelator characterized by IR, TGA, CPMAS C-13 NMR and elemental analyses. It has been used for enrichment of Cu(II), Zn(II), Fe(III), Ni(II), Co(II), Cd(II) and Pb(II) prior to their determination by flame atomic absorption spectrometry (FAAS). The pH ranges for quantitative sorption (98.0-99.4%) are 4.0-7.0, 5.0-6.0, 3.0-4.0, 5.0-7.0. 5.0-8.0, 7.0-8.0 and 4.0-5.0, respectively. The desorption was found quantitative with 0.5 mol dm(-3) HCl/HNO3 (for Pb). The sorption capacity of the matrix for the seven metal ions has been found in the range 85.3-186.2 mumol g(-1). The optimum flow rate of metal ion solution for quantitative sorption of metal onto pyrocatechol functionalized cellulose as determined by column method, is 2-6 cm(3) min(-1), whereas for desorption it is 2-4 cm(3) min(-1). The tolerance limits for NaCl, NaBr, NaI, NaNO3, Na2SO4, Na3PO4, humic acid, EDTA, ascorbic acid, citric acid, sodium tartrate, Ca(II) and Mg(II) in the sorption of all the seven metal ions are reported. Ascorbic acid is tolerable up to 0.8 mmol dm(-3) with Cu and Pb where as sodium tartrate does not interfere up to 0.6 mmol dm(-3) with Pb. There is no interference of NaBr, NaCl and NaNO3 up to a concentration of 0.5 mol dm(-3), in the sorption of Cu(II), Cd(II) and Fe(III) on to the chelating cellulose matrix The preconcentration factors are between 75 and 300 and t(1/2) values less than or equal to5 min for all the metal ions. Simultaneous sorption of Cu, Zn, Ni and Co is possible at pH 5.0 if their total concentration does not exceed lowest sorption capacity. The present matrix coupled with FAAS has been used to enrich and determine the seven metal ions in river and tap water samples (relative standard deviation (R.S.D.) 1.05-7.20%) and synthetic certified water sample SLRS-4 (NRC, Canada) with R.S.D. similar to2.03%. The cobalt present in pharmaceutical vitamin tablets was also preconcentrated on the modified cellulose and determined by FAAS (R.S.D. similar to1.87%). (C) 2003 Elsevier B.V. All rights reserved.