Colorimetric detection of gallic acid based on the enhanced oxidase‐like activity of floral‐like magnetic Fe3O4@MnO2

Abstract In this study, a colorimetric method was developed for rapid and sensitive determination of gallic acid (GA) by using floral‐like magnetic Fe 3 O 4 @MnO 2 composite material with enhanced oxidase‐like activity. Fe 3 O 4 @MnO 2 composite material is able to oxidize 3,3′,5,5′‐tetramethylbenzidine (TMB) to a blue product (oxTMB) with apparent color change and absorbance at 652 nm. GA can reduce the oxTMB yielding a fading blue color. Based on these results, a technique is proposed to detect GA quantitatively and qualitatively with UV–vis spectroscopy and bare eyes. A low detection limit of 0.105 μM and a detection range of 0.01 to 15 μM were obtained with UV–vis spectroscopy. This methodology possesses high potential for application in determination of GA.