Abstract: The invention relates to a method for preparing a sample for chromatographic separation processes, in which a sample vessel (1) is partially filled with a substance to be examined and is closed, the substance to be examined is subjected to a thermo-chemical reaction in which at least one sample component is converted into another substance, and in which by means of a removing device samples are removed from the sample vessel (1) for analytical examination, characterised in that the sample vessel (1) forms a cavity, into which the substance to be examined is introduced as a core and a heating section for indirect heat transfer is applied along the filling of substance to be examined.