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 x 10(-7) to 1.5 x 10(-6) M with a detection limit of 4.0 x 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 x 10(-6) M to 1.0 x 10(-5) M at lambda(max) = 600 nm with limit of detection of 4.7 x 10(-6) M and RSD of 1.8% for RB5 concentration of 1.0 x 10(-5) M.