A sample pre-compression valve (3) for liquid chromatography applications, comprising a circular stator (1) and a circular rotor (2) disposed adjacent to each other along their circular area and rotatable along their circular area, the stator having at least 5 ports A, B, C , D and E and the rotor has at least 2 grooves X and Y, wherein the grooves X and Y can each connect two of the ports A, B, C, D and E with each other, and wherein the ports may be punctiform or groove-shaped, wherein (i) in a position 1 of the valve, the groove X connects the ports A and B with each other such that there are no dead volumes in the groove X, and the groove Y connects or does not connect the ports C and D; and (ii) in a position 2 of the valve, the groove X connects the ports A and B such that there are dead volumes in the groove X, and the groove Y connects or does not connect the ports C and D; and (iii) in a position 3 of the valve, the groove X interconnects the ports A and E so that there are no dead volumes in the groove X, and the groove Y connects or does not connect the ports B and C, characterized in that in position 3 of the valve there are no dead volumes in the connecting grooves.
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