An electrochemical oxygen filter is described that removes efficiently dissolved oxygen from the surface of an electrochemical sensor. Simulations show that 99 % of oxygen can be removed in less than 60 s if an electrochemical filter made of a porous electrode is positioned at less than 200 µm from the sensor surface. For experimental demonstration, the metallic filter was made with either a stainless steel or a platinum grids separated from the sensor by a porous separator. It was combined with a sensor for analysis of paraquat, an herbicide widely used over the world. In aerated solutions, paraquat signal was not distinguished due to the strong interference of oxygen. When using the oxygen filter, paraquat was clearly detected with a better-defined response than the one obtained under N2 atmosphere that requires longer time before analysis.