Determinação Voltamétrica de Nitrito Empregando o Íon (Fe(CN)6) 3- como Mediador Eletroquímico

In this work, a voltammetric method for determination of nitrite in tap and mineral waters samples was developed. The method is based on the reduction of nitrite catalyzed by the electrochemical mediator (Fe(CN)6) 3- . A carbon paste electrode (CPE) prepared with solid paraffin as binder agent was used as working electrode and cyclic voltammetry was the voltammetric technique employed for nitrite quantification. All parameters of the analytical method were optimized and the best conditions obtained were: BR buffer 0.04 mol L -1 pH = 1.0 as supporting electrolyte and 0.7 mmol L -1 of Fe(CN)6) 3- in the electrochemical cell. Under these optimized conditions, the method presented a linear range from 0.05 to 2.5 mmol L -1 of nitrite, with limits of detection and quantification equal to 22 and 75 μmol L -1 , respectively. Spiked samples of mineral and tap water were analyzed by the proposed method and recovery percentages close to 100 % were obtained for all analyzed samples. Moreover, the method has presented a satisfactory precision since low values of relative standard deviation (RSD) were always obtained. These results indicate that the method allow the reliable determination of nitrite in water samples in a simple and inexpensive way.