Abstract: A sample injector is provided, which enables changing of the volume of the sample chamber between a very small volume and larger volumes. The injector includes a housing, a stator (16, FIG. 3) mounted in the housing, and a rotor(26) pivotally mounted in the housing, with the stator and rotor having facewise adjacent faces extending perpendicular to the pivot axis. First and second stators are alternately mountable in the housing, with the first stator having a disc element (44, FIG. 3) that includes a storage channel (62) in one of its faces to form an internal storage chamber of small volume. The other, alternate stator has at least one disc element (44X, FIG. 5) that includes a pair of through passages (52X, 56X) therein that are constructed to connect to sample ports (52, 56) of a disc element that hold the opposite ends of an external sample loop (90) to enable the injector to be used with a larger storage volume.