An apparatus for separating at least two discrete volumes of a composite liquid into at least a first component and a second component comprises a centrifuge, which comprises: - a rotor (32, 34, 35) having a rotation axis (31), comprising - at least two separation cells (40), each for containing a separation bag (1) containing a volume of composite liquid and - a first balancing means for balancing the rotor (32, 34, 35) when the respective weights of the at least two separation bags (1) in the at least two separation cells (40) are different.
