Abstract: A thick film electrochemical micro-sensor apparatus for detection and quantification of trace metal ions in water, comprising a substrate to which is applied an arrangement of electrodes comprising at least one of a first type of working electrode, at least one of a second type of working electrode, a counter electrode, a reference electrode, and optionally pH and temperature detectors. The apparatus is especially useful for detection and quantification of trace metal ions in water and effluent. A method of detecting and quantifying trace metal ions using the electrochemical micro-sensor apparatus is also described comprising contacting the water or effluent with the sensor of the present invention, applying a voltage selected for the trace metal ion to be detected, measuring the current output of the micro-sensor, determining if the current output indicates the presence of the trace metal ion, and generating a signal.