COMPARISON OF SUPERCRITICAL CARBON-DIOXIDE AND SUPERCRITICAL PROPANE AS MOBILE PHASES IN SUPERCRITICAL FLUID CHROMATOGRAPHY

Comparisons of supercritical propane and supercritical carbon dioxide eluents were made on bare silica and octadecylsilane-derivatized silica using substituted and unsubstituted aromatic hydrocarbons as test solutes. The greater elution strength of carbon dioxide relative to propane for these solutes on underivatized silica is indicated to be largely the result of more effective competitive adsorption by carbon dioxide rather than enhanced mobile phase solubility. The effects of the addition of methanol modifier on solute retention were more pronounced in propane for both polar and non-polar solutes. An increase in the retention of polar aromatics on silica was observed with increasing density in methanol modified propane. This is apparently the result of a concomitant increase in the availability of stationary phase adsorption sites. © 1990.