Arrangement and process for optical analysis and specific isolation of biological samples

A process for detecting cells to be detected in a liquid sample, comprising:

• i) filtrating the liquid sample through a porous membrane arrayed in a flat configuration on a transparent supporting body, wherein the porous membrane is suitable for retaining the cells to be detected, such that the cells to be detected are retained on at least part of a surface of the membrane and such that at least part of the liquid sample passes through the membrane, wherein the supporting body is a slide for microscopy, made of glass or plastic;
• ii) applying a liquid optical medium to the membrane on the transparent supporting body, wherein, the liquid optical medium has essentially the same refractive index as the transparent supporting body;
• and
• iii) optically measuring at least a subarea of the membrane on the transparent supporting body in order to detect the cells to be detected,
• wherein the porous membrane remains in a flat configuration on the transparent support during the entire course of steps i)-iii).