Simultaneous electrochemical determination of hydrazine and hydroxylamine on a thiadiazole derivative modified pencil graphite electrode

This work explores the fabrication of an electrochemical sensor for the simultaneous determination of hydrazine (HY) and hydroxylamine (HA) using a modified pencil graphite electrode (PGE). The PGE was modified by the electropolymerization of 2-amino-5-mercapto-1,3,4-thiadiazole (AMT) in an acidic medium. The modified electrode was characterized by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray analysis (EDX), atomic force microscopy (AFM), IR spectroscopy, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The developed sensor showed a linear range of 1.5 mM-167.42 mM and 0.5-167.42 mM for HY and HA respectively in 0.1 M KCl medium, which is higher than the reported literature for both analytes. The sensing device showed lower detection limits of 0.08 mM and 0.82 mM for HA and HY, respectively. The electrochemical oxidation of HA and HY on the modified electrode was found to be an irreversible diffusion-controlled reaction. The electroactive surface area and electron transfer rate constant of the modified electrode were also calculated. The bare PGE does not separate the voltammetric signals of HA and HY. However, the modified PGE was successful in resolving the oxidation peaks of HA and HY at 0.73V and 0.29 V. The electrochemical determination of both analytes was done by differential pulse voltammetric analysis (DPV). The sensor showed only negligible interference with some of the co-existing species of the analytes in the real sample. The repeatability, reproducibility and stability of the electrode were satisfactory with good recovery of the analytes from tap water and river water samples.