TRAPPING EFFICIENCY AND SOLUTE FOCUSING IN ONLINE SUPERCRITICAL-FLUID EXTRACTION CAPILLARY SUPERCRITICAL-FLUID CHROMATOGRAPHY

An on-line supercritical fluid extraction/capillary supercritical fluid chromatography system was developed using a capillary trap with stationary phase and a linear restrictor. With the system, samples can be injected into either the supercritical fluid chromatography (SFC) column or the trapping tube with the same injector, allowing rapid and accurate measurements of trapping efficiency. The self-cooling effect due to fluid expansion drastically improved the trapping efficiency. External cooling allowed quantitative collection of n-decane, provided that condensing of CO2 in the trap was avoided. Volatile solutes were more favorably refocused onto the SFC column at the lower column temperature. This system can also be used as a sample introduction method for volatile solutes.