[en] Analysis of stable and radioactive isotopes is essential as a complement to geochemistry and geohydraulic investigations on groundwater regimes and their genesis. This is widely acknowledged also for the determination of the specific activity of ⁸⁵Kr in groundwater. The geochemical inertness and well-defined input function of ⁸⁵Kr allow estimates of groundwater age and enhance characterization of groundwater flow and components in many aquifer systems. A new site for measurement of the ⁸⁵Kr specific activity has been established at the Institute of Applied Physics at the Freiberg University, Saxony. Under normal conditions ca. 80 μl krypton are dissolved in 1 m³ of water in contact with air. Therefore gas extraction has to be most effectively. A modified CO₂ extractor of 45 cm x 10 cm was chosen. The water is continuously pumped under pressure (3 - 4 bar) passing a Venturi-type nozzle, which simultaneously operates as a water-jet pump. The extracted gas flows through a CO₂ trap (NaOH 10 %), a H₂O cold trap, through molecular sieves (5, 3 A) and a charcoal column, cooled by liquid nitrogen, where krypton, nitrogene and other components are adsorbed. Remaining gases re-enter the extractor at the Venturi-type nozzle. A small membrane pump supports the circulation. Due to the special design of the water outlet, contamination of the sample is avoided. Optional a compact stove heats the water to improve the extraction efficiency. If pressure supply is high enough, additional extractors can be run simultaneously. In a test run the recovery for radon was around 65 to 70 %. Further preparation steps of the raw krypton sample is performed in the laboratory. To obtain a good first enrichment a tube furnace filled with chrome powder is used to separate nitrogen and oxygen from the sample at 900 deg C. The following enrichment steps are performed by a preparation setup developed at GSF-Institute for Hydrology, Neuherberg. (author)