In this work, detection of oxygen through its electrochemical reduction to hydrogen peroxide and subsequent detection by oxidation is investigated, using both gold and platinum IDEs to determine which material has a better performance at this scale. Fabrication of single metal IDEs requires fewer processing steps than a mixed metal IDE, therefore sensor devices comprising two IDEs were fabricated as either gold-gold or platinum-platinum. While gold is anticipated to be the superior metal in reducing DO, platinum was also explored as it may have the appropriate behaviour at the ultramicro scale to suit the desired detection method. Experiments were performed in generator-collector mode to reduce DO and to oxidise any hydrogen peroxide produced. Subsequently, both metal's ability to oxidise hydrogen peroxide was also tested to establish the preferred collector material. Parameters were established for the appropriate sensing technique, including the relevant pretreatment steps. Finally, the method was applied to detection of DO in estuarine river water samples and samples containing some common reductive interferents to establish the viability of the sensor in real world applications.