Multidimensional open-tubular column supercritical fluid chromatography using a flow-switching interface

A multidimensional system based on capillary supercritical fluid chromatography (SFC) was constructed that utilizes a simple flow‐switching interface between two open‐tubular 50‐μm i.d. columns. A novel solvent‐venting injection technique was incorporated in the system that enables single or multiple 0.5‐μL volumes to be injected into an uncoated, yet deactivated, length of capillary precolumn without flooding of the analytical column. The effectiveness of multidimensional capillary SFC (SFC‐SFC) for complex mixtures is demonstrated by the analysis of polycyclic aromatic hydrocarbons (PAH) in a coal tar extract, the trace determination of a methylcarbamate pesticide and its metabolites in a bird extract, and a group‐type separation of hydrocarbons in a high‐boiling petroleum distillate. These examples show for the first time that capillary SFC‐SFC is a complementary alternative to other multidimensional chromatographic methods involving liquid or gaseous mobile phases.