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 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 x 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 x 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.