Electrochemical reaction mechanism and determination of Sudan I at a multi wall carbon nanotubes modified glassy carbon electrode

A multi wall carbon nanotubes (MWCNT) modified glassy carbon electrode (GCE) was prepared by casting MWCNT suspension on the surface of the GCE. Evaporation of solvent from such a solution yielded robust surface film containing MWCNT. The electrochemical reaction mechanism of Sudan I was investigated at the MWCNT modified GCE (MWCNT/GCE) in phosphate buffer solution (PBS) with various pH values. Cyclic voltammetry, controlled-potential electrolysis studies showed the reduction of NN group in Sudan I yielded aniline and α-amino naphthol through hydrazo (an intermediate product). The process was proved to be the ECE mechanism. In addition, the MWCNT/GCE can greatly catalyze the oxidation of OH group in Sudan I with minimal electrode surface fouling. Consequently, an amperometric sensor for Sudan I was proposed. The sensor has excellent performance associated with high sensitivity (21.56 μA mM−1), low detection limit (3.46 × 10−8 M) and wide linear range (1.01 × 10−6–1.22 × 10−4 M) in addition to stable response. Finally, the method was successfully applied for the determination of Sudan I in ketchup samples with satisfying results.