We can manage without crude oil, but not without water. Hence, it is obvious that we should test water for possible contamination; not just drinking water but especially waste and surface water, in order to discover any contamination. The analysis can be complicated if the water contains a large proportion of suspended substances and foreign particles. Membrane extraction promises simplification in this case: a novel procedure for sample preparation developed by the Environmental Research Centre Leipzig-Halle, which has been licensed and brought into and perfected for series production by GERSTEL.