Abstract: An improvement in the method of injection of liquid into an industrial device for separation by gas chromatography by means of a vaporizer swept by a vector, the liquid being brought to the vaporizer by a pipe containing a valve which, when opened and closed, permits the injection at a given rate of flow, of the predetermined quantity of liquid, the rapid purge of the fluids contained in the vaporizer and the adjacent ducts at the end of the injection, and the continuous slow purge between injections being insured by a system of valves, wherein the instantaneous vaporization is insured by a vaporizer-exchanger, and a branch permits the vector gas to short-circuit the vaporizer when the injection is shut off, while feeding the column.