Chloromethylated polystyrene-divinylbenzene has been functionalized with dithiooxamide. The resulting chelating resin (DTOA) has been characterized by elemental analyses, infrared spectroscopy, thermogravimetric analysis, and metal ion sorption capacities. It has been used for the preconcentration and separation of Cu(II), Zn(II), Cd(II), and Pb(II) prior to their determination by FAAS. Parameters such as the amount of the resin, effect of pH, equilibration rate, sorption and desorption of metal ions, and effect of diverse ions have been studied. The maximum sorption capacities found are 0.97, 0.12, 0.08, and 0.12 mmol g(-1) for Cu(II), Zn(II), Cd(II), and Pb(II) at pH 6.0, 5.5, 1.0, and 5.5, respectively. The preconcentration factors are 100, 100, 50, and 50 for Cu(II), Zn(II), Cd(II), and Pb(II), respectively. Recoveries of the metal ions were 96 5, 97 +/- 6, 96 +/-5, and 96 +/- 5 at 95% confidence level, whereas the limits of detection are 2.0, 1.3, 2.5, and 25.0 mu g L-1 for Cu(II), Zn(II), Cd(II), and Pb(II), respectively. The calibration curves were linear up to 12 mu g mL(-1) (R-2=1.000), 2 mu g mL(-1) (R-2=0.998), 2 mu g ml(-1) (R-2=1.000), and 5 mu g mL(-1) (R-2=0.979) for Cu(II), Zn(II), Cd(II), and Pb(II), respectively. The reliability of the method has been tested by analyzing certified samples. (c) 2006 Wiley Periodicals, Inc. I Appl Polym Sci 103: 2281-2285, 2007