TiO2 preconcentration integrated with hydride generation-colorimetric system for the rapid and selective detection of Se(IV).

Selenium (Se) is an essential trace element for humans and the determination of Se(IV) in daily samples is of great significance. A low-cost, easy-used hydride generation-fluorescence colorimetric method was developed for the rapid and selective detection of Se(IV) using a silver-based metal-organic framework (Ag-PMDA) as a substrate. Se(IV) was converted into volatile H2Se via hydride generation. The generated H2Se then reacted with Ag-PMDA-modified test paper, causing the in-situ generation of Ag2Se nanoparticles on its surface. This resulted in a distinct fluorescence quenching and a visible color variation of the test paper. The resulting signal could be directly observed by the naked eye and further quantified using the smartphone RGB mode, which exhibited a linear range of 0-1.0 μg/mL (y = -438.77x+596.77, R2 = 0.9905). By incorporating a TiO2-based preconcentration step, the sensitivity was substantially enhanced, reducing the limit of detection from 0.019 μg/mL to 0.002 μg/mL. The method was successfully applied to the detection of Se(IV) in real water samples and selenium-enriched products, with recoveries ranging from 104 % to 110%. Owing to its simple operation, low cost, good anti-interference capability and portability, this method shows great potential for on-site analysis.