Voltammetric study of nitrofurazone in ionic liquids by using a carbon fiber microelectrode

Nitrofurazone (NF) exhibits a broad spectrum of biological action and the understanding of its reduction mechanism in aqueous media has been widely studied. The NF reduction was studied by cyclic (CV) and square-wave (SWV) voltammetric techniques having a homemade carbon fiber microelectrode and employing three different ionic liquids: 1-Butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BMImTf2N), 1-Ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMImTf2N) and 1-Butyl-3methylimidazolium tetrafluoroborate (BMImBF4). The NF reduction behavior was similar for the three ionic liquids used, being a single cathodic peak (-0.623 V, -0.742 V and -0.760 V in BMImBF4, BMImTf2N and EMImTf2N, respectively) recorded by SWV. However, only the SW voltammograms obtained in BMImBF4 and BMImTf2N showed that the net currents are composed by the forward and backward components, which indicates the existence of a reversible system (Figs. 1A and 1B). Similarly, this reversibility also could be observed by CV, since a reversible redox couple was recorded for the NF reduction in the same ionic liquids (Figs. 1C and 1D). From the frequency variation by SWV it was observed that the cathodic peak potential values were practically kept constant and that the net currents varied linearly with the frequency square-root, confirming a reversible system with adsorption of the reagent and product on the electrode surface. Based on this behavior, it was possible to calculate the number of electrons involved in the NF reduction in BMImBF4 and BMImTf2N, reaching values between 0.8 and 0. 9, indicating clearly a nitro-anion radical generation.