Electrochemical Sensor for Simultaneous Measurement of Nitrite and Superoxide Anion Radical Using Superoxide Dismutase-Mimetic Manganese(III) Tetrakis(1-methyl-4-pyridyl)Porphyrin on Polypyrrole Matrix

An electrochemical highly sensitive nitrite (NO^– ₂ and superoxide anion radical (O•₂ ^–) sensor was fabricated and developed based on an electrochemical deposition of manganese(III) tetrakis(1-methyl-4-pyridyl)porphyrin (MnTMPyP) in polypyrrole (PPy) matrix on Pt electrode. The surface morphological image of MnTMPyP-PPy and PPy matrix on Pt electrode was obtained by scanning electron microscopy exhibiting microporous structure. The electrochemical behavior of the MnTMPyP-PPy-Pt electrode as sensor investigated by cyclic voltammetry revealed that the characteristic of MnTMPyP reversible redox peaks obtained at –0.12 V and –0.38 V versus Ag/AgCl respectively. The sensor electrode showed an excellent electrocatalytic nitrite oxidase and superoxide dismutase (SOD) activities. This electrochemical sensor exhibited a linear current response over the concentration range from 0.8 to 1000 μM, with a detection limit of 0.8±0.03 μM for NO^– ₂ and a corresponding linear range from 0.6 to 1000 μM, with a detection limit of 0.6 ± 0.02 μM for O•₂ ^–. In addition, the sensor displayed high sensitivity, good reproducibility and retained stability over a period of ∼4 weeks. This SOD-mimetic electrode was proved to be effective not only in detecting NO^– ₂ and O•₂ ^– independently but also in determining the concentrations of NO – 2and O•₂ ^– simultaneously in in vitro systems.