Dialysis cell for an in-vitro release test apparatus for determining a release behaviour such as a release rate of a substance of a material composition such as a drug, wherein the substance is bound to molecular carriers such as liposomes, micelles or nanoparticles with respect to a substance uptake fluid, comprising: - a cell interior and a dialysis membrane at least partially delimiting the cell interior, which - holds the bound substance back, - is permeable for substance released into the substance uptake fluid and - is at least partly permeable for the substance uptake fluid - a support structure, wherein the dialysis membrane is attached to the support structure, which is designed for fixed mounting of the dialysis cell at a mounting position that is immobile relative to the in-vitro release test apparatus, wherein the support structure includes - a retaining enclosure and - a mounting element which is designed for attachment to the apparatus, which - is embodied as a mounting plate with an outer ring flange by which the support structure can be fastened detachably to the in-vitro release test apparatus, and - the mounting element is fastened to the retaining enclosure detachably as a separate component with regard to the retaining enclosure in such manner that the dialysis membrane is clamped between the retaining enclosure and the mounting element, thereby forming a sealing surface which completely surrounds the cell interior, closing it off from an outside area of the support structure, characterized in that - the mounting element - has a passage for a drivetrain extending in axial direction, such as a driveshaft for operating an internal agitator unit which is to be disposed in the cell interior, and - a cylindrical mounting surface, which preferably faces radially outwardly, and a cylindrical sealing surface which preferably faces radially inwardly towards the retaining enclosure, wherein the retaining enclosure comprises a cylindrical mating sealing surface with a shape adapted to the sealing surface and facing radially outwards, wherein the dialysis membrane is clamped between the sealing surface and the mating sealing surface. - a cell interior and a dialysis membrane at least partially delimiting the cell interior, which - holds the bound substance back, - is permeable for substance released into the substance uptake fluid and - is at least partly permeable for the substance uptake fluid - holds the bound substance back, - is permeable for substance released into the substance uptake fluid and - is at least partly permeable for the substance uptake fluid - a support structure, wherein the dialysis membrane is attached to the support structure, which is designed for fixed mounting of the dialysis cell at a mounting position that is immobile relative to the in-vitro release test apparatus, wherein the support structure includes - a retaining enclosure and - a mounting element which is designed for attachment to the apparatus, which - is embodied as a mounting plate with an outer ring flange by which the support structure can be fastened detachably to the in-vitro release test apparatus, and - the mounting element is fastened to the retaining enclosure detachably as a separate component with regard to the retaining enclosure in such manner that the dialysis membrane is clamped between the retaining enclosure and the mounting element, thereby forming a sealing surface which completely surrounds the cell interior, closing it off from an outside area of the support structure, characterized in that - is embodied as a mounting plate with an outer ring flange by which the support structure can be fastened detachably to the in-vitro release test apparatus, and - the mounting element is fastened to the retaining enclosure detachably as a separate component with regard to the retaining enclosure in such manner that the dialysis membrane is clamped between the retaining enclosure and the mounting element, thereby forming a sealing surface which completely surrounds the cell interior, closing it off from an outside area of the support structure, - the mounting element - has a passage for a drivetrain extending in axial direction, such as a driveshaft for operating an internal agitator unit which is to be disposed in the cell interior, and - a cylindrical mounting surface, which preferably faces radially outwardly, and a cylindrical sealing surface which preferably faces radially inwardly towards the retaining enclosure, wherein the retaining enclosure comprises a cylindrical mating sealing surface with a shape adapted to the sealing surface and facing radially outwards, wherein the dialysis membrane is clamped between the sealing surface and the mating sealing surface. - has a passage for a drivetrain extending in axial direction, such as a driveshaft for operating an internal agitator unit which is to be disposed in the cell interior, and - a cylindrical mounting surface, which preferably faces radially outwardly, and a cylindrical sealing surface which preferably faces radially inwardly towards the retaining enclosure, wherein the retaining enclosure comprises a cylindrical mating sealing surface with a shape adapted to the sealing surface and facing radially outwards, wherein the dialysis membrane is clamped between the sealing surface and the mating sealing surface.