Visual and quantitative determination of dopamine based on CoxFe3-xO4 magnetic nanoparticles as peroxidase mimetics

In this study, cobalt doped magnetic composite nanoparticles (CoxFe3-xO4 MNPs) were firstly prepared through a simple and convenient coprecipitation approach. The characterization results from EDX, ICP-AES, TEM, XRD and XPS showed that the cobalt atoms might be located in the lattice position instead of the part of iron atoms. CoxFe3-xO4 MNPs possessed higher peroxidase-like activity comparing with Fe3O4 MNPs, although they were similar in crystal structure, size distribution and morphology. The as-prepared nanomaterials could effectively catalyze the reaction between 3,3,5,5-tetramethylbenzidine (TMB) and H2O2 under 40 degrees C within 15 min. Dopamine (DA) has some reducibility due to the existence of phenol hydroxyl group, which results in it can consume H2O2 and cause the blue shallowing of the reaction solution between H2O2 and TMB. A visual, sensitive and simple colorimetric method based on CoxFe3-xO4 MNPs as peroxidase mimetics was developed for detecting DA. Good linear relationship and recoveries for DA were obtained from 0.6 to 8.0 mu M and 98.7 to 101.0%, respectively. The limit of detection (LOD) of the proposed method was calculated as 0.13 mu M. And the relative standard deviation (RSD) was less than 4.0%. The visual method was successfully applied to DA detection in Common Yam Rhizome (Shan Yao) and human serum sample. (C) 2013 Elsevier B.V. All rights reserved.