1. Field of the Invention
The invention relates to a filtration container, in particular for concentration of macromolecules, said filtration container being insertable into a filtrate recovery tube and comprising an upper portion, a central portion axially adjoining the upper portion, and a lower portion axially adjoining the central portion, of which                the upper portion forms a sample container, which is hollow-cylindrical and has an inlet opening on its upper end face,        the downwardly tapering central portion a filtration chamber, which has two mutually opposed main walls running downwardly towards one another and also two gusset-like connection walls connecting said main walls at the lateral edges thereof, at least one of the main walls having a filter window for receiving a planar membrane filter, and        the lower portion forms a retentate chamber adjoining the lower edge of the filter window, the defining main walls and connection walls of said retentate chamber being planar extensions of the main walls and connection walls of the central portion.        
2. Description of the Related Art
Macromolecules, in particular protein samples, are concentrated in a volume range from 500 μl to 20 ml in filtration containers, which are inserted into a filtrate recovery tube and are concentrated in centrifugal units via the method of ultrafiltration. In the case of ultrafiltration, it is normal to provide a retentate chamber in the form of what is known as a dead stop pocket in the filtration containers, this being intended to prevent the sample from running dry. Here, the concentrated sample is collected in the dead volume formed by the retentate chamber and is recovered again by pipetting.
The recovery of the entire concentrate is very critical, since the volume is very small. This means that losses of just a few microliters lead to high percentage losses of the final yields.
EP 0 651 675 B1 discloses a filtration container for concentration of macromolecules, which, in conjunction with a filtrate recovery tube and a microconcentrating device for concentrating macromolecules from a solution by rotation of the microconcentrating device in a centrifuge, collects the concentrated macromolecules in a retentate container. The known filtration container consists of an upper portion, a central portion axially adjoining the upper portion, and an axially adjoining lower portion. Here, the upper portion forms a sample container, which is hollow-cylindrical, and the downwardly tapering central portion forms a filtration chamber, which has two mutually opposed main walls running downwardly towards one another and also two connection walls connecting said main walls at the lateral edges thereof. One of the main walls here forms a filter window for receiving a flat membrane filter. The adjoining lower portion forms a retentate chamber, which adjoins the lower edge of the filter window and of which the defining main walls and connection walls are planar extensions of the main walls and connection walls of the central portion.
Although this known device has proven its worth in principle, it has been found that complete sample recovery is very difficult.
Furthermore, a filtration container for centrifugal concentration of macromolecules is known from JP 62-11564 A1. A substantially hollow-cylindrical container has a cylindrical insert that divides the container in the longitudinal direction and has a sealing collar. Here, a beveled attachment is arranged above the collar and its entry opening is covered by a filter membrane, which therefore rises by an angle between 25 and 45°. Here, an annular retentate chamber is formed between the attachment and the surrounding container wall, and the retentate is collected in said retentate chamber.
With this device too, a complete and defined sample recovery has proven to be very difficult.
The object of the present invention is therefore to specify a filtration container that has a retentate chamber and that enables practically complete sample recovery.