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

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.