A rotary valve used in chromatography includes a stator with a plurality of stator ports arranged on the stator. The stator further includes a stator groove connected at one end to a first stator port and terminating between the first stator port and a second stator port adjacent to the first stator port. A rotor, rotatably fitted to the stator, has a plurality of arcuate channels arranged in an asymmetrical pattern on the rotor. Each rotor channel connects to one or more of the stator ports. Different connections of the rotor channels to the stator ports produce at least three different positions for the injection valve. The three different positions provide a complete chromatography sample injection sequence using only a single valve.
