In this work, a simple, rapid, selective, sensitive and economical method has been developed for the simultaneous separation and preconcentration of trace amounts of copper, nickel, cadmium, and zinc in aqueous medium using XAD-4 resins that were modified with 2-(5-bromo-2pyridylazo)-5-diethylaminophenol (5-Br-PADAP) as an analytical reagent. The sorption is quantitative in the pH range 7.0-9.5, whereas quantitative desorption occurs instantaneously with 2 M HCl and selected trace elements have

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... been determined using flame atomic absorption spectrometry. The linearity is maintained between 0.04-4.0 mg L -1 for copper, 0.1-4.0 mg L -1 for nickel, 0.02-1.3 mg L -1 for cadmium and 0.01-1.4 mg L -1 for zinc. The detection limits were 12 µg L -1 for Cu(II), 30 µg L -1 for Ni(II), 6 µg L -1 for Cd(II), and 4 µg L -1 for Zn(II) in the final solution. Various parameters such as the effect of pH, flow rate, breakthrough volume and interference of a large number of anions and cations have been studied and the proposed method was used for determination of these metal ions in water and standard samples. In order to compare the proposed method, the actual water samples were analyzed by direct FAAS (using standard addition method). Determination of these metal ions in standard samples confirmed that the proposed method has good accuracy.