Ultrasensitive determination of selenium by atomic fluorescence spectrometry using nano-TiO2 pre-concentration and in situ hydride generation

An ultrasensitive, simple and interference-free method using nano-TiO2 preconcentration and in situ slurry hydride generation (HG) coupled with atomic fluorescence spectrometry (AFS) was developed for the determination of trace selenium. Total Se reduced in Se(IV) form can be selectively adsorbed on TiO2 at pH < 8 for pre-concentration, and then separated and slurried/released by a mixture containing 3% (m/v) KBH4 and 1% (m/v) KOH. The slurry solution was mixed with 25% (v/v) HCl to generate selenium hydrides, which was subsequently separated from the liquid phase for subsequent AFS detection. Optimum conditions for adsorption, disadsorption and hydride generation of selenium as well as potential interferences from concomitant ions were investigated. Due to the repulsive force between the positively charged TiO2 and metal cationic ions, this approach permits 1000 mg L-1 for Fe3+, Ni2+ and Co2+, 500 mg L-1 for Cu2+ or 100 mg L-1 for Ag+ and Au3+ present in a 5 mu g L-1 Se(IV) solution without any significant interferences. A limit of detection of 0.0006 mu g L-1 was obtained by sampling a 40 mL sample solution. Compared to the conventional HG method, the sensitivity and the limit of detection were improved 17- and 16-fold by the present method, respectively. The proposed method was successfully applied for the determination of trace selenium in several real samples.