Use of Amberlite XAD-2 loaded with 1-(2-pyridylazo)-2-naphthol as a preconcentration system for river water prior to determination of Cu2+, Cd2+ and Pb2+ by flame atomic absorption spectroscopy

A procedure for separation and preconcentration of trace amounts of copper(II), cadmium(II) and lead(II) in river water samples is proposed. The procedure is based on the adsorption of Cu2+, Cd2+ and Pb2+ ions on a column of Amberlite XAD-2 resin loaded with 1-(2-pyridylazo)-2-naphthol (PAN) reagent prior to their determination by flame atomic absorption spectrometry (FAAS). Sorption is quantitative in the pH range of 6.0-8.5 for Cu, 7.5-8.5 for Cd and 8.0-11.0 for Pb; the optimum pH for simultaneous retention was 8.5. Quantitative desorption for Cu2+ occurs in a 2-3 M HCl or 2-3 M HNO3 medium, for Cd2+ in a 2-4 M HCl or 0.5-3 M HNO3 medium, and only with 3 M HNO3 for Pb2+. The sorption capacity of the resin was 0.1081, 0.0228, and 0.0065 mmole g(-1) of the dry Amberlite-PAN for Cu2+, Cd2+ and Pb2+, respectively. The simultaneous determination of three cations is possible using 3 M HNO3 as an eluent. The limit of tolerance of some electrolytes were also studied. The highest preconcentration factor obtained was 50. The precision of the method, evaluated as the relative standard deviation obtained by analyzing a series of seven replicates, was below 5% for all three elements. The standard addition technique was used and analytical results achieved for Simulated Fresh Water IAEA W-4, a standard reference material, were in good agreement with certified values. The proposed procedure was applied to the analysis of different river water samples using flame AAS.