COMPOSITION AND DENSITY EFFECTS USING METHANOL CARBON-DIOXIDE IN PACKED-COLUMN SUPERCRITICAL FLUID CHROMATOGRAPHY

The density of mixtures of carbon dioxide with 0-11.5 mol % methanol was measured at 40 °C, between 80 and 200 bar. Chromatograms were run at constant density but varying composition and at constant composition but varying density. For the systems studied, changing fluid composition provides wider adjustment of solute retention than density changes. Plots of log k' vs percent modifier, at constant density, were nonlinear. However, plots of log k' vs mobile phase solvent strength, as measured using the solvatochromic dye Nile Red, produced a linear relationship. The change in retention vs the pore volume (proportional to surface area) was also measured. © 1990, American Chemical Society. All rights reserved.