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. HNO3 (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 μmol g−1 and loading half time (t1/2) 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 ∼2.6–12.8%) and tap (RSD ∼1.8–7.2%) water samples.