On-chip Electrochemical Detection of Dissolved Oxygen: Eliminating the Requirement for Permeable Selective Membrane

Dissolved Oxygen (DO) quantification is an important measure of the overall health of a water system. Fluctuations from normal values can indicate the presence of contaminants, and predict further events, for example, fish deaths resulting from eutrophication. DO can vary due to a variety of environmental factors, including altitude, so regular monitoring is crucial to understanding the baseline water conditions. Electrochemical approaches offer good accuracy and ease of use but are currently limited by their requirement for an oxygen permeable membrane to remove interference. To this end, we propose the use of interdigitated electrode arrays to facilitate the quantification of DO, without the need for a membrane, by measuring the by-product of the oxygen reduction reaction: hydrogen peroxide. In this paper, we show the use of mixed metal electrode arrays to sufficiently produce, and subsequently quantify, hydrogen peroxide as a proxy measure of dissolved oxygen, with a detection limit of 0.36 ppm DO. We further show that this technique is adequate for the detection of DO in tidal river water, and can be reliably used in the presence of chlorine and iron, which have electrochemical activity in the same potential range.