Thesis (M.Sc.)--Chulalongkorn University, 2010

A method for on-line preconcentration and determination of Pb(II) by flame atomic absorption spectrometry was developed. The solid phase extraction was applied in the preconcentration and silica gel chemically modified with 3-mercaptopropyltrimethoxysilane (Si-MPTS) was used as column packing material. The Si-MPTS was synthesized and characterized by fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). In the determination of Pb(II), the sample solution (10 mL) was passed through the column with a flow rate of 9.0 mL min-1. The sorbed Pb(II) ions were eluted with 200 µL of 0.05 mol L-1 HCl solution at a flow rate of 1.4 mL min-1. The preconcentration factor of 50 and sample throughput of 37 samples h-1 were achieved. The performance of the system was investigated under the optimum conditions using the solution containing 20 and 100 µg L-1 of Pb(II). The percentage recovery and the precision (%RSD) of the method were 102.2-106.8% and 4.8 -10.2 %, respectively. The accuracy of the method was tested by using certified reference material (SRM 1643e). The proposed system was applied for the determination of trace levels of Pb(II) in water samples.