Determination of trace metals in natural samples by ICP-OES after preconcentration on modified silica gel and on modified silica nanoparticles

Silica gel and nanometer SiO2 modified with 4-(2-aminoethylamino)-N-(2-(2-aminoethyl amino)ethyl)butanamide (SG-AAEB and nanometer SiO2-AAEB), which were prepared based on chemical immobilization, were used as sorbents for the solid phase extraction of Cu(II), Fe(III), and Pb(II) prior to their determination by inductively coupled plasma optical emission spectrometry. Adsorption efficiencies of the two sorbents towards metal ions were investigated by batch and column procedures. For both sorbents the preconcentration conditions of analytes including effects of pH, shaking time, sample flow rate and adsorption capacity, were investigated and compared. The differences of silica gel and nanometer SiO2 in sizes and surface structures resulted in distinct chemical activity and selectivity toward metals. At pH 4, the adsorption capacity of SG-AAEB was found to be 12.2, 14.5 and 9.8 mg g(-1) for Cu(II), Fe(III), and Pb(II), respectively. In comparison, nanometer SiO2-AAEB showed a high selectivity toward Pb(II) and has a much larger adsorption capacity (22.3 mg g(-1)). Furthermore, the application of SG-AAEB and nanometer SiO2-AAEB for simultaneous preconcentration of trace Cu(II), Fe(III), and Pb(II) from natural samples was performed with satisfactory results.