Surface silica was modified with 3-aminopropyltriethoxysilane [(C2H5O)(3)-Si(CH2)(3)NH2] to get amino-modified silica. Surface characteristics and surface area of the silica-gel before and after chemical modification were determined by elemental and surface area analysis. Silica-gel modified with 3-aminopropyltriethoxysilane has been developed for the preconcentration of cobalt and nickel prior to their determination by graphite furnace atomic absorption spectrometry. Batch and column methods were used for the separation and concentration of cobalt and nickel. The experimental parameters, such as the effect of pH of the sample, shaking time in batch technique, flow rate of the eluent and the amount of silica, on retention and elution have been investigated. Cobalt and nickel were successfully recovered from brine (up to 1% NaCl) and sea-water samples.