A method and device for analyzing samples containing mixtures of organic compounds using vacuum chromatography is disclosed. The method and device are particularly useful for obtaining mass spectra for identification purposes. The method involves passing a sample dissolved in a solvent through a column with a carrier gas and depositing a thin layer of the sample in the interior of a short column. The short column is then attached to an MS interface. The device comprises a combination of a variable molecular separator and a column alignment component. The alignment component may also be used as a direct probe injector. This device and method allow the separation and MS analysis of mixtures of intermediate molecular weight compounds.