The coprecipitation method is widely used for the preconcentration of trace metal ions prior to their determination by flame atomic absorption spectrometry (FAAS). A simple and sensitive method based on coprecipitation of Fe(III) and Ni(II) ions with Cu(II)-4-(2-pyridylazo)-resorcinol was developed. The analytical parameters including pH, amount of copper (II), amount of reagent, sample volume, etc., were examined. It was found that the metal ions studied were quantitatively coprecipitated in the pH range of 5.0-6.5. The detection limits (DL) (n = 10, 3s/b) were found to be 0.68 mu g L(-1) for Fe(III) and 0.43 mu g L(-1) for Ni(II) and the relative standard deviations (RSD) were <= 4.0%. The proposed method was validated by the analysis of three certified reference materials (TMDA 54.4 fortified lake water, SRM 1568a rice flour, and GBW07605 tea) and recovery tests. The method was successfully applied to sea water, lake water, and various food samples.