A device for sealing a reagent container storing and providing liquids, in particular in an analyzer system. The invention also relates to a reagent container using such device for sealing, a cartridge for holding such reagent container, and a method for removing a liquid from such reagent container. The instant invention provides a device for sealing a reagent container comprising an annular member configured to be inserted into the reagent container, wherein the annular member is configured to being movably coupled to the reagent container relative to its longitudinal center axis; an opening passing from a top end of the annular member to a bottom end of the annular member; and a sealing element arranged between the top end and the bottom end of the annular member for sealing the opening.