Modifier effects on column efficiency in packed-column supercritical fluid chromatography

We investigate the effects on column efficiency of methanol, acetonitrile, ethanol, and 1-propanol used as modifiers in packed-column SFC. C-18, phenyl, and cyano columns were used with both nonpolar and polar solutes. For highly retained nonpolar solutes, addition of modifier significantly increased apparent column efficiency, especially for the C-18 column. For polar solutes, the presence of modifier dramatically improved retention and efficiency with an apparent efficiency dependence on modifier type and amount. Temperature and pressure effects on efficiency were also studied.