Flower-like β-Bi2O3 microsphere/multiwalled carbon nanotube composite for sensitive detection of carcinogenic Rhodamine B in chili oil

Rhodamine B (RhB) is highly carcinogenic and is therefore prohibited as a food colorant. Hence, it is necessary to establish a simple but effective technique for the sensitive determination of RhB in foodstuff. Herein, an efficient voltammetric platform was established for the detection of RhB in chili oil based on flower-like β-Bi 2 O 3 microsphere/multiwalled carbon nanotube composites (β-Bi 2 O 3 /MWCNTs). Various microscopic and spectroscopic techniques confirmed the successful formation of β-Bi 2 O 3 /MWCNTs. Owing to the synergistic effect from β-Bi 2 O 3 microspheres and MWCNTs, the β-Bi 2 O 3 /MWCNTs demonstrated superior electrocatalytic activity for the oxidation of RhB as compared to the individual components. Electrochemical kinetics tests confirmed that the RhB electrooxidation was governed by an irreversible and adsorption-controlled process, and involved two electrons one proton transfer pathway. The oxidation peak currents of RhB were linearly correlated with RhB concentrations ranging from 0.05 to 100 μM with a low limit of detection (0.002 μM). The β-Bi 2 O 3 /MWCNT demonstrated strong anti-interfering ability against other azo colorants, and retained robust voltammetric responses for at least 14 days. Moreover, the concentrations of RhB in chili oil were accurately detected by the β-Bi 2 O 3 /MWCNT via second-order derivative linear scan voltammetry with satisfactory recovery. Overall, the β-Bi 2 O 3 /MWCNT/GCE shows great potential for in-situ analysis of trace amounts of RhB in various food matrices.