Samples of ADW with varying concentrations of oxygen were prepared by purging ADW solutions with nitrogen for 30 minutes. After purging, the ADW samples were covered with parafilm which contained a small perforation. This allowed oxygen to partition back into solution, albeit at a slow rate. It was found that oxygen typically re-dissolved at a rate of approximately 1 ppm per 3 minutes when the concentration was between 0 and 4 ppm. After 4 ppm was reached, the rate slowed down to 1 ppm per 7 minutes until a 6 ppm concentration was reached. To bring the solution back to saturated concentrations, oxygen had to be bubbled into the solution, as the time to reach saturation by diffusion was considerably longer. This resulted in ADW solutions with various oxygen concentration between fully nitrogen purged (~0.5 ppm), and fully saturated (~8.8 ppm). All oxygen concentrations were first measured using a commercial optical DO probe (Hach, LDO101). CV was performed for each concentration, using the Au-Pt mixed metal IDE, in the voltage window of 1.2 V to -0.8 V vs. Ag/AgCl. The Au generator was scanned while the Pt collector was biased at 0.4 V to oxidise the generated hydrogen peroxide. Prior to any scan, the Pt collector was biased at -0.8 V for 20 seconds as a pretreatment step to remove any oxide that may have formed on the surface of the Pt electrode Detection of Dissolved O2 in the Presence of Known and Unknown Interferents Samples of ADW were spiked with 1 mg/L iron (FeCl3, Sigma Aldrich) and 1 mg/L chlorine (NaOCl, Milton Sterilizing Fluid), both of which are known to be active interferents in the oxygen reduction window. The method described above was used to test these samples to determine how both the generator and collector electrodes would be affected by the presence of additional reacting species. Furthermore, samples of river water (taken from River Lee, Cork) were tested using the same approach. The spiked samples were measured versus a blank ADW sample with an equivalent concentration of DO, as measured by the optical DO probe. Similarly, the river water was tested versus a sample of ADW with equivalent concentrations of DO, while also being kept at the same temperature.