Modification of Amberlite XAD-4 resin with 1,8-diaminonaphthalene for solid phase extraction of copper, cadmium and lead, and its application to determination of these metals in dairy cow’s milk

A new chelating resin was synthesized by modification of Amberlite XAD-4 resin with 1,8-diaminonaphthalene through an azo linkage (NN). The synthesized resin was characterized by scanning electron microscope, Fourier transform infrared spectroscope, elemental analysis and thermogravimetric analysis. It was applied to preconcentrate and separate Cu(II), Cd(II) and Pb(II) ions, which were determined subsequently by graphite furnace atomic absorption spectrometry. Various physico-chemical parameters that influence the quantitative preconcentration and recovery of the metals were optimized by both static and dynamic techniques. Among them, optimum pH was in the range 6–7. 2.0 M HNO3 was selected as eluent. Optimum flow rates of sample and the eluent were found to be 2 and 4 mL min−1, respectively. Preconcentration factors were 220 for Cu(II) and Cd(II) and 240 for Pb(II), sorption half times (t1/2) were 5 min for Cu(II) and Cd(II) and 6 min for Pb(II), respectively. The Langmuir, Freundlich and Temkin adsorption isotherms were also studied in detail. The procedure was validated by analysis of a certified reference material (A-11, powder milk). The new method was employed to estimate the metal ion concentrations quantitatively from dairy cow’s milk collected from dairy farm, Savar, Dhaka, Bangladesh.