Selective trace analysis of bismuth in water and sediment samples based on solid phase extraction using a modified silica gel containing oxygen and nitrogen donor atoms

A new selective method is described for the solid phase extraction and preconcentration of trace level bismuth in aqueous solutions by using gallic acid modified silica gel (GASG) in a acidic medium (pH 1.0) prior to determination by flame atomic absorption spectrometry (FAAS). In the column experiments, Bi(III) can be adsorbed on gallic acid modified silica gel at pH 1.0 with 94.69 % retention, whereas the retention of other common coexisting metal ions such as Pb(II), Cd(II), Cu(II), Zn(II), Co(II), Ni(II), Mn(II) and Fe(III) is less than 10 %. The adsorption equilibration for Bi(III) was achieved within 10 min. At optimum conditions, the adsorption capacity of the extractant is 7.25-7.73 mg/g, preconcentration factor is 250 and detection limit is 0.26 ng/mL. Gallic acid modified silica gel is stable in 4 mol/L HCl-pH 7.0 buffer solutions. The procedure was validated by analysis of a standard reference sediment material (GBW07350, China). The new solid phase extractant has been used for the preconcentration of low level of Bi(III) in lake sediment, wastewater and lake water samples, recoveries of 95.4-101 % were obtained. It is shown that low level of Bi(III) can be effectively preconcentrated by this new selective solid phase extractant.