Development of comprehensive two-dimensional packed column supercritical fluid chromatography

A comprehensive two-dimensional supercritical fluid chromatographic system with conventional packed columns was developed. The system used a computer-controlled ten-port valve, a capillary trap, and a restrictor. The mobile phase was pure carbon dioxide. The first dimension column was operated under constant pressure in the stopped-flow mode, while the second dimension column was operated in the constant flow mode. The effluent of the first column was depressurized through the restrictor and solute was trapped within the capillary trap. Then the trapped solute was transferred into the second column by switching the valve. Since the solute transfer process is very rapid, the valve can be switched back after a short injection period in order to collect next fraction. This allowed the sampling time to be changed without changing any of the other conditions, such as the second dimension run time. The system was applied to the separation of triglycerides in fats and oils. Separations were performed using the same ODS packing materials for both columns, and the first column was operated under subcritical conditions and the second column under supercritical conditions.