Separation of Anilines, Benzamides, Benzylamines, and Phenylethylamines by Packed-Column Supercritical Fluid Chromatography

Organic nitrogen-containing compounds, including primary aliphatic amines, were rapidly and efficiently separated on a silica-based Diol column with methanol—carbon dioxide mixtures containing isopropylamine as a very polar additive. Reduced plate heights were as low as 1.75. Total efficiency sometimes approached 28,000 theoretical plates (in 1.6 min), and nearly 300 plates per second were generated. The relative retention of anilines, benzamides, benzylamines, and phenylethylamines was studied. The same mix was also separated on a polymer-based Asahipack amino column without additive. The solutes all eluted from the polymer-based column; but peaks tailed significantly and apparent efficiency was low.