Radioactive materials emit ionizing radiation that, even in minuscule amounts, can be harmful to health and environment, and permanently damage human tissue genetic material. This is why liquid waste at hospitals, mining facilities, nuclear reprocessing plants and radioactive waste repositories require continuous, in-situ monitoring in real time. This invention, a measuring device from the Technical University of Dortmund, detects radioactive isotopes emitting alpha radiation in liquid samples. Using microfluidic components, the aqueous sample is first passed through a filtering chamber, then into the detection chamber comprising a semiconductor detector and an MEMS heater. These components are protected by a chemically inert diamond coating between 20 nm and 1 µm in thickness. With this measuring device, radioactive material in close proximity to the detector is concentrated, which significantly increases signal strength. After measurement, the detection chamber is electrochemically sanitized. With this type of device, wastewater and groundwater in particular can be tested.