Abstract: An apparatus for controllably and reproducibly introducing, small amounts of a liquid sample into chromatographic systems, especially high resolution gas chromatographic systems with cold injection, thin-layer chromatographic systems and high resolution liquid chromatographic systems, in order to obtain sampling extremely reduced in volume and presenting maximum reliability and reproducibility, uses a sample container having a pipette-like or nozzle-like outlet neck of very small diameter. The liquid placed in the container is submitted to at least one pressure pulse which is controlled in duration and/or amplitude in order to determine emission of a corresponding and controlled quantity of liquid from the outlet neck.