Quantitative analysis involves percolation of a gas on a porous material to produce the fixed phase which is measured for a solid fixed phase by absorption chromatography and for a liquid fixed phase by separation chromatography. Blood alcohol levels can be measured from blood samples at the same time as enzyme levels. The technique is also used for detection of sodium n-dipropylacetate (Depakine) to monitor the treatment of epileptics, for separation of benzodiazepine I-4, from body fluids and for verification of sympathomimetic amines in blood and of barbiturates, carbamazepine, or methalqualone in urine. Chromatographic determination of blood methane and butane levels can be useful in establishing cases of suicide. The technique has proved especially useful in pinpointing the origin of particular hashish types. The latter efforts must consider factors affecting test samples such as variation in genetic potential within the same countries, variations in resins produced by the same seeds depending on the place of cultivation or on harvest condititions in the various regions, and methods of preparation. Development of equipment less fragile than that previously used has rendered the techniques more feasible for criminalistic purposes. --in French.