Abstract: The invention provides a method of operating a chromatographic apparatus for separating a fluid mixture. The apparatus has a plurality of compartments containing a chromatographic packing, conduit means interconnecting the compartments in at least one closed loop series, isolating valves in said conduits for isolating each compartment from the remaining compartments, and, for each compartment, a valved purge fluid inlet, a valved purge fluid outlet, a valved carrier fluid inlet, a valved carrier fluid outlet, and a valved fluid mixture inlet. The valved fluid mixture inlet is adapted to be coupled to a source of a fluid mixture to be separated chromatographically.