Electrochemical Study of Vinylsulphone Azo Dye Reactive Black 5 and Its Determination at a Glassy Carbon Electrode

The electrochemical oxidation of vinylsulphone azo dye, Reactive Black 5 (RB5), at a glassy carbon electrode has been carried out in phosphate buffer solutions in the pH range 2.85–11.79 employing cyclic voltammetry (CV) and differential pulse voltammetry (DPV). RB5 showed one well-defined oxidation peak at 0.560 V vs. Ag-AgCl using DPV. The oxidation process was shown to be irreversible over the pH range 2.85–8.39 and was diffusion controlled. The linear relationship between the peak current height and RB5 concentrations allowed the differential pulse voltammetric determination of the dye over a wide concentration range, from 6.0 × 10−7 to 1.5 × 10−6 M with a detection limit of 4.0 × 10−7 M. The precision and recovery did not exceed 4.9 and 98.2%, respectively. A UV-Vis spectrophotometry method was also proposed for the determination of the RB5 in concentration range from 5.0 × 10−6 M to 1.0 × 10−5 M at λmax = 600 nm with limit of detection of 4.7 × 10−6 M and RSD of 1.8% for RB5 concentration of 1.0 × 10−5 M.