A novel colorimetric detection method based on the peroxidase-like activity of metal-substituted polyoxometalates (POMs) of SiW₉M₃ (M = Co2+, Fe3+, Cu2+, Mn2+) has been established. POMs can catalyze oxidation of dopamine (DA) and ractopamine (RAC) by H₂O₂ in aqueous solutions. SiW₉Co₃-based POMs detect DA at concentrations as low as 5.38 × 10−6 mol·L−1 simply by observation of the color change from colorless to orange using the naked eye. RAC is detected by observing the change from colorless to slight red by SiW₉Cu₃ with a detection limit of 7.94 × 10−5 mol·L−1. This study shows that colorimetric DA and RAC detection using SiW₉Co₃ and SiW₉Cu₃ is highly selective and sensitive as well as visually observable.
Keywords: colorimetric detection; dopamine; peroxidase-like; polyoxometalates; ractopamine.