Gas chromatography in which sample is absorbed in inlet evaporation tube

In a new procedure for separating substances using gas chromatography, in a first mode of operation a controlled flushing gas flow (4) is passed through sample inlet system (1) consisting of an evaporation tube (18) which contains a selective phase and/or packing material. The test material, which consists of a solvent which contains the substances to be separated, is fed (3) into this flushing gas flow. In this mode of operation, the inlet (8) to the separation column (9) is closed, for example by a pneumatic device (14), and the flushing gas together with any test material which is not retained in the evaporation tube is removed (11) from the system.In a second mode of operation, the inlet to the separation column is open, and a carrier gas conveys the test material which has been retained in the evaporation tube, and is now released by thermal desorption, into the column.During the first mode of operation, at least one of the following parameters: rate of test material dosing, temperature in the evaporation tube, and flow rate of flushing gas, is controlled in relation to one or other of the remaining two parameters. The novel feature is that this control is exercised in such a way that the test material passes through the evaporation tube in a mostly liquid form, and before switching over to the second mode of operation any residual solvent in the evaporation tube is vaporised and is removed by the flushing gas.