DETERMINATION OF THE HOLD-UP TIME AND COLUMN OUTLET DENSITY FOR CAPILLARY SUPERCRITICAL FLUID CHROMATOGRAPHY

The column hold-up time (t(u)) was determined for a capillary supercritical fluid chromatographic system over a range of temperatures and densities using methane as a marker and using homologous series extrapolations. At low temperatures, t(u) was found to pass through a maximum with increasing density. To establish that this phenomenon is not due to a retention effect, t(u) was also calculated from flow-rate measurements. The measured hold-up times and Darcy's law were used to calculate the outlet densities for different inlet pressures at two temperatures.