USE OF A THERMALLY INSULATED COLUMN FOR IMPROVED SPEED, EFFICIENCY AND RESOLUTION IN PACKED-COLUMN SUPERCRITICAL FLUID CHROMATOGRAPHY

摘要

The use of a thermally insulated column for significant improvements in speed, efficiency and resolution in packed-column supercritical fluid chromatography at intermediate mobile: phase densities is demonstrated. Elution of a mixture of normal alkanes, containing 12 to 18 carbon atoms from a 150x2.0-mm I.D. column packed with 5-mu m porous octylsilica particles, was performed with carbon dioxide mobile phase at 50 degrees C at reduced densities of 1.0 and 1.5. For elution of n-octadecane at a reduced density of 1.0, a two-to sixteen-fold increase in the apparent number of theoretical plates was observed for an insulated column compared to the uninsulated column at pressure drops of 12 and 29 bar, respectively, along with decreased retention times and improved resolution. The improved efficiency obtained with an insulated column at the lower density is due to the effective elimination of radial temperature gradients associated with expansion and cooling of the mobile phase. The insulated column provided no measurable improvement at the higher density. (C) 1997 Elsevier Science B.V