Fabrication of Metal-Substituted Polyoxometalates for Colorimetric Detection of Dopamine and Ractopamine

A novel colorimetric detection method based on the peroxidase-like activity of metal-substituted polyoxometalates (POMs) of SiW(9)M(3) (M = Co(2+), Fe(3+), Cu(2+), Mn(2+)) has been established. POMs can catalyze oxidation of dopamine (DA) and ractopamine (RAC) by H(2)O(2) in aqueous solutions. SiW(9)Co(3)-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 SiW(9)Cu(3) with a detection limit of 7.94 × 10(−5) mol·L(−1). This study shows that colorimetric DA and RAC detection using SiW(9)Co(3) and SiW(9)Cu(3) is highly selective and sensitive as well as visually observable.