A sample injector includes a rotary valve element with a straight passageway through it, which element may be rotated to connect a port communicating with a source of solvent with a port communicating with an inlet to a column. Another passageway connects two adjacent ports. The valve element may be rotated to one position in which it provides a straight path for sample to be injected, a second position in which it provides a path that connects a source of purge gas to the chromatographic system and a third position in which it provides a path that connects solvent to the column for preconditioning.