Development of a methyl thymol blue-loaded alginate hydrogel for the quantitative RGB detection of Sr(II) ions in water

Abstract Detecting Sr(II) in water is crucial due to health risks such as bone disorders and Sr-90’s cancer-related effects. This study developed a methyl thymol blue (MTB)-loaded alginate hydrogel for sensitive, on-site colorimetric detection. Biocompatible Na-Alginate hydrogels encapsulate MTB, which changes color upon Sr(II) interaction. Optimized conditions include pH, temperature, and ion concentration. Red-Green-Blue analysis using smartphones showed a a linear increase in the blue channel for 1–10 mgL −1 Sr(II), which was further confirmed by UV–Vis absorption peaks at 440 nm and 600 nm. The structural and chemical characterization of the hydrogel beads was performed using SEM, EDX, and FTIR analyses, confirming their morphology, elemental composition, and functional groups. This simple method enables real-time Sr(II) monitoring in water.