Thesis (M.Sc.)--Chulalongkorn University, 2007

Silica gel was chemically modified firstly with 3-aminopropyltriethoxysilane giving SiAP. the SiAP reacted subsequently with 1,8-diaminoanthraquinone obtaining SiDAAQ. The SiDAAQ was characterized by specific surface area analysis, IR-spectroscopy, UV-visible spectrophotometry, elemental analysis and ¹³C-NMR. The adsorption properties of the SiDAAQ were studied using Cd(II), Co(II), Cu(II), Ni(II), Pb(II) and Zn(II) in aqueous solutions with batch and column modes. The on-line preconcentration system coupled with FAAS for Pb(II) was investigated. The sorbed lead ions were directly eluted by 174 µL of 0.050 mol L⁻¹ EDTA solution (pH5) at a flow rate of 5.0 mL min⁻¹ to the nebulizer. The performance characteristics of the system were investigated under the optimum chemical and flow parameters using the solutions containing the spiked standard 100 and 300 µg L⁻¹ Pb(II). The method detection limit of 20 µg L⁻¹ with enrichment factor of 27 and the sample throughput of 40 h⁻¹ at preconcentration time of 60 sec were obtained. The accuracy and precision evaluated as %recovery and %RSD (n = 10) were 100.8 and 10.8, respectively. The proposed system was successfully applied for the determination of trace levels of Pb(II) in water sample.