Anodic Oxidation of Nitrite at a Molybdenum Oxide Layer

Abstract

The anodic oxidation of nitrite at a glassy carbon surface modified by a molybdenum oxide layer electrochemically deposited is discussed. The results demonstrated that at certain thickness values the film is permeable to small substrates like iodide and nitrite. On the other hand, at anhydrous films (prepared by vacuum evaporation) no electrochemical response for nitrite was observed in experiments performed in a CH3CN solution, confirming the relationship between the porosity of the film and its water content. Voltammetric curves recorded in alkaline solutions showed an enhanced response for the oxidation of nitrite when the electrode surface is modified with the MoO3 film, which is nonconductive at the working potential range. The current enhancement is probably associated with an entrapment of NO2 (electrogenerated in a first step) at the electrode/film interface, the MoO3 sites transferring an O-atom in a further step. The modified electrode was used as an amperometric sensor for nitrite in a flow injection configuration, the method being applicable in the range 5 to 1000 μM at a potential of 1.0 V. The repeatability of the analysis is around 3 % and the lower limit of detection is 1 μM. The method was used in the determination of nitrite in sausage samples with a recovery of 104 %.