Retention of acidic and basic compounds in packed column supercritical fluid chromatography

Abstract

Retention behaviour in supercritical fluid chromatography (SFC) with packed columns has been investigated using various model compounds of different polarity. Capacity ratios and selectivities were determined for basic compounds (xanthine bases), fat-soluble vitamins and carboxylic acids. Many of these compounds are difficult to elute from packed columns when a nonpolar supercritical fluid is used. In this work mobile phases of carbon dioxide and nitrous oxide with alcohol modifiers (methanol and 2-propanol) were used. The dependence of capacity ratios and selectivites on the modifier content of the mobile phase was measured. Retention behaviour of the model compounds was compared for stationary phases of unmodified and chemically modified silica particles. The results can be summarized in some general guidelines for stationary phase selection in packed column SFC.