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

In this study, cobalt doped magnetic composite nanoparticles (Co x Fe 3− x O 4 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. Co x Fe 3− x O 4 MNPs possessed higher peroxidase-like activity comparing with Fe 3 O 4 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 H 2 O 2 under 40 °C within 15 min. Dopamine (DA) has some reducibility due to the existence of phenol hydroxyl group, which results in it can consume H 2 O 2 and cause the blue shallowing of the reaction solution between H 2 O 2 and TMB. A visual, sensitive and simple colorimetric method based on Co x Fe 3− x O 4 MNPs as peroxidase mimetics was developed for detecting DA. Good linear relationship and recoveries for DA were obtained from 0.6 to 8.0 μM and 98.7 to 101.0%, respectively. The limit of detection (LOD) of the proposed method was calculated as 0.13 μM. 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.