Simultaneous detection of hydrazine, sulfite, and nitrite based on a nanoporous gold microelectrode

Abstract

Quality control is a critical aspect in the food industry, where it is of high importance to maintain the level of additives such as sulfite (SO32−) and nitrite (NO2−) within the permissible limits. Gold (Au) remains one of the most recurrently used and sought-after materials for the fabrication of microelectrodes, and serves as a reinforcement material in biosensors. A nanoporous gold microelectrode synthesized by employing an electrochemical alloying/dealloying method was used for the determination of hydrazine (N2H4), SO32−, and NO2−. The fabricated microelectrode was characterized via scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX). Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were utilized to investigate the electrochemical behaviors of the nanoporous gold microelectrode. The electrochemically active surface area (EASA) of the gold microelectrode was significantly enhanced by 25 times via the alloying/dealloying treatment. The nanoporous gold microelectrode exhibited high activity towards the simultaneous electrochemical oxidation of N2H4, SO32−, and NO2− with well separated peaks centered at 0.05, 0.34 and 0.76 V, respectively. A wide linear range of 5.0 to 4000 μM with the R2 value over 0.993 was achieved; and very low limits of detection (LOD) were found to be 9.11 × 10−7, 3.37 × 10−7, and 1.44 × 10-6 mol L−1 for the electrochemical determination of N2H4, SO32−, and NO2−, respectively. The nanoporous gold microelectrode possessed the high selectivity and stability. The performance of the electrochemical sensor was further validated using real samples such as water, wine, apple cider beer, and beef with good recovery rates, thereby exhibiting its probable application in food safety and quality control.