Abstract: Sampling and analyzing at least one mixture of substances by slab chromatography or thin layer chromatography involves sampling the mixture on a non-adsorbent solid support using a sampling member to achieve precisely repeatable conditions, depositing an appropriate amount of the mixture to be analyzed on an edge zone of a chromatography plate, bringing the said edge of the chromatography plate into contact with a solvent or a mixture of solvents to cause the migration of the mixture on the chromatography plate and the separation of the constituents of the said mixture, and developing the said plate for the qualitative and/or quantitative analysis of the constituents of the mixture, by pressing that face of the support which bears the mixture against the chromatography plate until the mixture to be analyzed has essentially migrated entirely out of the abovementioned support.