Abstract: An electrochemical sensor array for detecting analytes in water, including a frame; a plurality of sensor electrodes each mounted to the frame, including a free chlorine working electrode including a gold thin film and having a free chlorine sensing surface to be exposed to the water; and a reference electrode including a silver thin film and a silver and silver chloride layer and having a reference sensing surface to be exposed to the water. A method of manufacturing an electrochemical sensor array for detecting analytes in water, including forming a free chlorine electrode, including forming a gold thin film on a first base layer; forming a reference electrode, including forming a silver thin film on a second base layer and applying a silver and silver chloride paste to a portion of the silver thin film; and arranging the free chlorine electrode and the reference electrode on a common frame.