Nitrite is a ubiquitous pollutant in modern society. Developing new strategies for its determination is very important, and electroanalytical methods present outstanding performance on this task. However, the use of bare electrodes is not recommended because of their predisposition to poisoning and passivation. We herein report a procedure to overcome these limitations on carbon fiber microelectrodes through pulsed amperometry. A three-pulse amperometry approach was used to reduce the current decay from 47% (after 20 min under constant potential) to virtually 0%. Repeatability and reproducibility were found to have an RSD lower than 0.5% and 7%, respectively. Tap water and synthetic inorganic saliva samples were fortified with nitrite, and the results obtained with the proposed sensor were in good agreement with the amount added.

A nanoporous gold (NPG) surface with high electroactive surface area and roughness factor was prepared via anodizationelectrochemical reduction method and was used as a new platform to study the electrochemical oxidation of hydrogen peroxide (H 2 O 2 ). Field-emission scanning electron microscopy (FE-SEM) analysis, cyclic voltammetry, and amperometry techniques were employed for structural morphology and electrochemical studies. The H 2 O 2 oxidation peak potential was significantly shifted (∼0.23 V) towards a less positive direction with increased current response at the NPG surface compared to that of a bare gold electrode. The mechanism for the H 2 O 2 anodic oxidation at the NPG surface was proposed based on the calculated transfer coefficient (α = 0.32) and the total number of electrons involved (n = 2.0) in the electrochemical process. Besides, the diffusion coefficient (D) of H 2 O 2 in PBS solution was also calculated using the Randles-Sevcik equation (2.18 × 10 −5 cm 2 s −1 ). In addition, the analytical application of the NPG electrode was demonstrated by amperometric detection of H 2 O 2 at a relatively less positive potential (0.57 V). The current increased proportionally to H 2 O 2 concentration in the linear range of 0.01 to 1.8 mM and the detection limit was found to be 0.6 μM (S/N = 3).

No abstract