Electrocatalytic oxidation and amperometric determination of hydrazine using a carbon paste electrode modified with β-nickel hydroxide nanoplatelets.

β-Nickel hydroxide nanoplatelets (NPs) were synthesized and used as a modifier on a carbon paste electrode (CPE) for the detection of hydrazine. Synthesis is based on a one-step hydrothermal method using L-arginine that acts as an agent to adjust the pH value and to shape the NPs. They were characterized by field emission scanning electron microscopy, X-ray diffraction and energy-dispersive X-ray spectroscopy. The composition of the modified electrode was optimized by changing the amount of NPs. Best results were achieved using a 10:70:20 weight ratio for nanoparticles, graphite and mineral oil (the binder). The electrochemical properties of the modified CPE were studied by cyclic voltammetry. The surface coverage of the NPs, the electron transfer coefficient and the charge transfer rate constant were calculated. The diffusion coefficient of hydrazine is 1.56 × 10-5 cm2 s-1. An amperometric method was worked out that has the following figures of merit: (a) A working applied potential of 500 mV (vs. Ag/AgCl reference electrode), (b) a linear range that extends from 1 to 1300 μmol L-1, (c) a 0.28 μmol L-1 detection limit, (d) a relative standard deviation of 1.3% (for n = 3 at a level of 5 μmol L-1), and (d) a sensitivity of 1.33 μA μmol-1 L cm-2. The performance of the sensor is compared to other nickel-based sensors for hydrazine. The sensor was successfully used to quantify hydrazine in spiked tap water samples, and the recoveries were 97 ± 2.3% (n = 3). Graphical abstract Schematic presentation of hydrazine electrocatalytic oxidation on NP.CPE*. *NP-CPE (β-nickel hydroxide nanoplatelet modified carbon paste electrode).