Modifier effects on column efficiency in packed column supercritical fluidchromatography

We investigate the effects on column efficiency of methanol, acetonitrile, ethanol, and 1-propanol used as modifiers in packed-column SFC. C-18, pheny l, and cyano columns were used with both nonpolar and polar solutes. For hi ghly retained nonpolar solutes, addition of modifier significantly increase d apparent column efficiency, especially for the C-18 column. For polar sol utes, the presence of modifier dramatically improved retention and efficien cy with an apparent efficiency dependence on modifier type and amount. Temp erature and pressure effects on efficiency were also studied.