We first screened for potential cross-reactions between the scavenger system and the sensing enzymes immobilized on glassy carbon electrodes in the osmium complex modified hydrogel film using cyclic voltammetry. Similarly to glucose oxidase (Figure ), the lactate oxidase modified electrode did not generate any catalytic current in the presence of paraformaldehyde (Figure ). Upon addition of lactate, a catalytic wave was observed corresponding to lactate oxidation by lactate oxidase and electron mediation through the Os-complex-modified polymer to the electrode (Figure ). The catalytic current in presence of paraformaldehyde declined with a half-life of at least two hours (Figure ). This time scale is largely sufficient for pointof-use lactate sensing via coulometry, which typically occurs within 10 min. These results confirm the absence of unwanted cross-reactions, demonstrating the compatibility between the paraformaldehyde-based oxygen scavenger and the lactate-sensing electrode.