Electrocatalytic Activity of L-Cystine towards the Sensitive and Simultaneous Measurement of Nitrobenzene and 4-Nitrophenol: A Voltammetric Study

A new simple, sensitive and selective electrochemical method for the determination of Nitrobenzene (NB) and 4-Nitrophenol (4-NP) at L-Cystine modified glassy carbon electrode was developed with the help of cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. Based on the effect of pH, a detailed electrochemical redox mechanism was proposed and the number of electrons involved in the R-NO2→ R-NO2¯● step was determined. The kinetic parameters such as heterogeneous rate constants (ks) and charge transfer coefficient (α) values were calculated and was found to be as 0.711×10-6 s-1, 1.486×10-6 s-1 and 0.521, 0.501 for both NB and 4-NP respectively. The NB and 4-NP systems were controlled by diffusion process and the diffusion coefficients values were determined as 3.24×10-7 cm2/s and 7.04×10-7 cm2/s for NB and 4-NP respectively. The limit of detection (LOD) and limit of quantification (LOQ) values were evaluated as 7.46×10-6 M, 24.9×10-6 M with linear dynamic range from 30 μM to 105 μM for NB and 0.1049×10-6 M, 0.349×10-6 M with linear dynamic range from 0.5 μM to 6 μM for 4-NP respectively. The developed method was effectively applied for the simultaneous determination of NB and 4-NP. Moreover the surface nature of the electrode was investigated by the electrochemical impedance spectroscopy. Finally the developed method was successfully applied for the real sample analysis with satisfactory recovery values having low RSD values.