Preconcentration of lead with Amberlite XAD-2 and Amberlite XAD-7 based chelating resins for its determination by flame atomic absorption spectrometry

Four chelating matrices prepared by coupling Amberlite XAD-2 with chromotropic acid (AXAD-2-CA or 1), pyrocatechol (AXAD-2-PC or 2) and thiosalicylic acid (AXAD-2-TSA or 3) through azo spacer and impregnation of Amberlite XAD-7 with xylenol orange (AXAD-7-XO or 4) have been studied for enrichment of lead(II). All the four resins quantitatively sorb Pb(II) at pH 3.0-8.0 when the flow rate is maintained between 2 and 10 ml min(-1). HNO, (0.5-4.0 M) instantaneously elutes Pb(II) from all the four chelating resins. The sorption capacity is in the range 16.0-186.0 mumol g(-1) and loading half time (t(1/2)) between 3.2 and 15.5 min. The tolerance limits of electrolytes (NaCl, NaBr, NaNO3, Na2SO4, Na3PO4) and cations (Ca and Mg) are reported. Phosphate interferes in the sorption with 3 and 4. The limit of detection and limit of quantification have been found to be in the ranges 2.44-7.87 and 2.76-8.64 ng ml(-1), respectively. Lead has been determined in river (RSD similar to2.6-12.8%) and tap (RSD similar to1.8-7.2%) water samples. (C) 2002 Elsevier Science B.V. All rights reserved.