Simultaneous superoxide and hydrogen peroxide detection in peroxidase/NADH oscillator

A dual enzyme-based amperometric sensor was applied to simultaneous detection of superoxide radical and hydrogen peroxide in the peroxidase/NADH oscillator. Both species were detected at nanomolar concentrations. Concentration–time profiles for superoxide and hydrogen peroxide closely resembled qualitative and quantitative model predictions except during periods of large-d[O2]/dt. Introduction of the sensor did not cause perturbation of the chemical behavior of the system within the reproducibility of the standard oscillator. Trace oxygen reduction on the sensorsʹ glassy carbon surfaces was minimized by setting biasing potentials of both sensors to E=+170 mV (vs. WO3 reference electrode). Characterization of hydrogen peroxide and superoxide sensorsʹ membranes was performed by Fourier Transform-Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy, and electrochemistry.