The invention relates to a dialysis method of recovering foreign substances, particularly low-molecular weight inorganic and/or organic substances, from semipermeable membrane of varying length and dimensions, using a PLE (pressurized liquid extraction) apparatus. The membranes are preferably in the form of a tube, for example semipermeable membrane devices (SPMDs) which, in the form of passive samplers, accumulate foreign substances/pollutants on an absorbent or adsorbent.