Voltammetric determination of hydrazine on glassy carbon electrode in aqueous solutions

Hydrazine is widely used as a fuel in rocket engines. It is also used as an intermediate in the production of medicines and agricultural chemicals, fibers, and antioxidants; to remove oxygen from the heating system; as polymerization catalyst; a means for purging process units; for application of metal coatings on glass and plastic, in photography and gas purification. Preventing the emission of hydrazine to the environment, mainly with wastewater, is an important problem. Maximum allowable concentration of hydrazine in water reservoirs of sanitary-domestic use is 0.01 dm. Methods for purification of wastewater from hydrazine may be based on its ability to decomposition and electrooxidation. Methods of electrochemistry are considered effective for the direct determination of hydrazine. Methods are known of voltammetry determination of hydrazine on glassy carbon electrodes or carbon paste electrodes, modified metals (gold, platinum, palladium, copper, iron, etc.). They are based on electrocatalytic oxidation of hydrazine in the presence of catalysts that are embedded into the electrode. Graphite nanotubes and various organic compounds are also used as modifiers. Existing voltammetric methods for determining hydrazine are complicated by the procedures of preparation (modification) of working electrode and addition of organic reagents to the background solution. Therefore, it was necessary to develop a technique of voltammetric determination using common electrodes requiring no additional and long preparation before the analysis (glassy carbon electrode, Au-graphite electrode) and maintaining the sensitivity and selectivity of the assay. The present work describes the choice of conditions for direct voltammetric determination of hydrazine in aqueous solutions and the development of a simple, sensitive, inexpensive and express method. We received an analytical signal of hydrazine on glassy carbon electrode in 0.1M KCl and 0.002 M NaOH at the potential of +0.4V in relation to an Ag/AgCl (KClsat) electrode as a reference electrode. The optimum conditions are: the accumulation potential -0.2 V, the scan rate 50 mV/s, the differential mode. The range of detectable concentrations of hydrazine in aqueous solutions is 0.04-1.00 dm. The cyclic voltammetry technique helped to set the irreversible process of hydrazine oxidation on the electrode. The correctness of the developed technique was tested by the analysis of spiked samples. The technique is suitable to monitor the content of hydrazine in catalytic processes of wastewater.

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