A clamping device for clamping a plurality of columns for sample preparation provides a plurality of clamping blocks and a displacement mechanism for displacing at least one clamping block relative to an opposing clamping block between an open position and a clamping position. At least three clamping blocks are retained in a row one behind the other on a guiding rail so that at least two columns can be clamped in an axial direction one behind the other between the clamping blocks. First and second slidingly displaceable clamping blocks of the least three clamping blocks are retained on the guiding rail and connected to the displacement mechanism by coupling means so that an actuation of the displacement mechanism from the clamping position into the open position brings about a displacement of all the slidingly displaceable clamping blocks and the columns are released.