COMPARISON OF 1,1,1,2-TETRAFLUOROETHANE AND CARBON DIOXIDE-BASED MOBILE PHASES FOR PACKED-COLUMN SUPERCRITICAL-FLUID CHROMATOGRAPHY

Highly polar, homogeneous mobile phases have a number of advantages ov er carbon dioxide-based mixed mobile phases for supercritical fluid ch romatography. While these fluids have been demonstrated to have very h igh eluotropic strengths in capillary systems, their utility for packe d columns lies in their ability to overcome the deleterious effects of residual silanol groups present on the bonded-phase surface. A partic ularly promising fluid, 1,1,1,2-tetrafluoroethane (HFC-134a), is chara cterized with respect to eluotropic strength, selectivity, efficiency and temperature effects. These results are compared to those obtained with carbon dioxide and methanol-modified carbon dioxide mobile phases on a silica column. HFC-134a displays different selectivities, effici encies, eluotropic strength and temperature dependencies on retention than either of the two reference mobile phases. (C) 1997 Elsevier Scie nce B.V.