Voltammetric method for determining hydrazine at a composite polymer-carbon electrode modified with gold particles

Abstract

Relevance. Hydrazine and its derivatives are used in the production of corrosion inhibitors, medicines, pesticides, dyes, polymers, components of energy production and storage systems, rocket fuels. The prospect of replacing carbon fuels with hydrazine is associated with its high calorific value and the formation of environmentally friendly oxidation end products (nitrogen, water). A serious disadvantage limiting the widespread use of hydrazine is its high toxicity. When exposed to the human and animal body, hydrazine and its compounds have carcinogenic and mutagenic effects, affect the central nervous system, and cause anemia. In this regard, the development of new and improvement of existing methods for the determination of hydrazine and its compounds in environmental objects, technological and biological environments is an urgent task. Aim. To establish the possibility of voltammetric determining hydrazine in solutions using a composite polymer-carbon electrode modified with gold particles. Objects. Solutions of hydrazine salts; aqueous solutions of acids, alkalis and salts. Methods. DC voltammetry, scanning electron microscopy, X-ray spectral microanalysis, computational modeling of ion-molecular equilibria. Results. The oxidation of hydrazine in solutions of N2H4×H2SO4+0.1 М KNO3 on a polymer-carbon electrode modified with gold particles under conditions of voltammetry with linear potential sweep proceeds at potentials E>0.3 V (vs. Ag/AgCl/KCl electrode) with a pronounced maximum current of anodic oxidation in the range of 0.5...0.9 V. Hydrazine oxidation on a modified electrode proceeds at low potentials due to the manifestation of the effect of electrocatalysis. It is established that the delayed stage of the electrode process is single-electron transfer. The reaction is of the first order in terms of hydrazine, is irreversible and is controlled by the diffusion of the substrate to the electrode surface. Based on the results of the analysis of the dependence of the maximum value of the hydrazine oxidation current on the modified electrode on the conditions of voltammetry (solution concentration, potential sweep rate, pH), a method for determining hydrazine in solutions is proposed. The following conditions for recording voltammograms are optimal: nitrogen deaerated background electrolyte 0.1 M KNO3, pH=5...7, the potential range for recording an analytical signal is 0.2...1.0 V, the potential sweep rate is 50 mV/s. Under these conditions, the dependence of the maximum value of the anodic oxidation current on the hydrazine concentration is described by linear regression equations in the ranges of 1×10–5…1×10–4 and 1×10–4…1.5×10–3 M N2H4 (the detection limit is 2.1×10–6 M). In comparison with the electrodes known from the literature, the modified electrode used in the work does not require a costly preparation and storage procedure, according to its analytical characteristics, the proposed method is not inferior to the most highly sensitive electrochemical methods for determining hydrazine.