Interferences from oxygen reduction reactions in bioelectroanalytical measurements: the case study of nitrate and nitrite biosensors

Bioelectroanalytical procedures based on cathodic processes are often subject to interference from dissolved oxygen. At the potentials applied for analyte detection, oxygen reduction may occur directly at the electrode or may be catalyzed by the electron mediators or the sensing enzyme of the biosensor. These processes affect the background current and may thus result in erroneous analyte quantification. In this review, current strategies to circumvent these oxygen interferences are presented and critically assessed with respect to their compatibility for on-site monitoring with amperometric biosensing devices operating at low potential. The main strategies consist in (1) use of oxygen scavenging systems to remove dissolved oxygen from the sample, (2) design of bioelectroanalytical approaches to shift the applied potential for analyte detection to more positive values, and (3) development of electrode materials to increase the overpotential for the oxygen reduction reaction. The latest developments in these approaches have recently led to the first biosensing devices based on reductases fully compatible with on-site monitoring requirements and this opens up possibilities for their widespread application.