an autosampler for high - performance liquid chromatography with a high - pressure injection valve having improved life , particularly in high pressure operation . the geometry of the valve components and the connections of the high - pressure injection valve are provided such that the switching processes do not take place in a deleterious direction . the grooves in rotor and / or the port opening cross sections in stator and the rotational direction are selected such that fluid flows from grooves under high pressure in the direction of narrow , substantially pressure - free ports are avoided . this applies in particular to the switching process from inject to load , since the sample loop contains a relatively large dead volume of compressed fluid . in addition , the valve can be controlled according to the invention in such a manner that an appropriate time is available for reducing harmful or undesired pressure differences .