Determination of trace silver in water by flame atomic adsorption spectrometry after separation/preconcentration with nanometer SiO_2

A new method for the determination of trace Ag based on nanometer SiO2 separation/preconcentration and flame atomic adsorption spectrometric(FAAS) determination was studied.The optimum conditions for adsorption were studied in detail including the effect of pH on adsorption ratio,adsorption time,elution conditions and effect of interference ions.It was fond that Ag+ could be adsorbed quantitatively on nanometer SiO2 at pH 4.1 and the adsorbed silver could be eluted with 0.5 mol/L HCl and 0.5 mol/L thiourea.A linear response of silver was obtained in the range from 0.005 to 1.5 μg/mL with the limit of detection of 0.77 ng/mL(3σ,n=11).The relative standard deviation under the optimum conditions was 3.6%(n=7,ρ=0.5 μg/mL) and the recoveries of silver were 94.0%～101.5%.The method has been applied to the determination of trace silver in environmental water samples with satisfactory results.