A silver nanoparticle-based colorimetric assay of trace selenium with hydride generation for sample introduction

A highly selective, sensitive yet simple colorimetric assay was developed for Se(IV) detection based on the silver nanoparticles (AgNPs), with hydride generation for separation and sample introduction. The proposed method could be easily performed by introducing the hydride vapor of the analyte (H2Se) into a thioglycolic acid (TGA) capped AgNPs solution. A combination of experimental and theoretical studies was used to illustrate the mechanism of this AgNPs colorimetric assay. The strong interaction of AgNPs with Se0 (oxidation product of H2Se) and/or H2Se weakens the stabilizing effect of TGA on AgNPs, leading to the aggregation of AgNPs and thus the color change of the AgNPs solution from bright yellow to light yellow or even colorless with the increase of Se(IV) concentration. The limit of detection was found to be 5 μg L−1 with UV-vis spectrophotometric detection, and 50 μg L−1 with the naked eye visual observation. The proposed method showed excellent selectivity and was successfully applied for Se(IV) determination in fish protein and sea water samples.