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Surface silica was modified with 3-aminopropyltriethoxysilane [(C2H5O)3-Si(CH2)3NH2] 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.

The method described uses the separation of As(III) and As(V) species in aqueous samples by means of the anion-exchange resin Amberlite IRA-93. The samples were acidified using acetic acid and passed through a glass column filled with pre-treated Amberlite IRA-93 resin. As(III) was poorly adsorbed on the anionic exchanger material, whereas As(V) was retained. The arsenic concentration was measured in the column effluent by graphite furnace AAS (GF-AAS). The retained As(V) was eluted from the column using 1 M NaOH. Prior to the determination of the As(V) concentration in the NaOH eluate, the eluate was passed through a glass column filled with a cation-exchange resin (Amberlite 200) to remove sodium ions and minimize the Na + interference with the AAS determination. After calibration the method was applied to the separation ofAs(III) and As(V) species in two aqueous extracts of arsenic contaminated soils. The results were compared with those obtained from an on-line separation and determination of As(III) and As(V) in the aqueous soil extracts using a state of the art HPLC-ICP-MS system.