Unique selectivity of perfluorinated stationary phases with 2,2,2-trifluoroethanol as organic mobile phase modifier

The selectivity of Luna C-18, Xterra (TM) C-18 and Fluophase (perfluorinate d C-6) stationary phases has been investigated with aqueous acetonitrile, m ethanol and 2,2,2-trifluoroethanol mobile phases using linear solvation equ ations. The gradient retention times of a set of 60 compounds with known mo lecular descriptors have been determined. Linear solvation equations have b een set up to describe the relationship between the gradient retention time s and the molecular properties. The selectivity of the stationary phase/mob ile phase systems was characterised by the regression coefficients of the m olecular descriptors. The perfluorinated stationary phase showed very diffe rent selectivity using 2,2,2-trifluoroethanol (TFE) as co-solvent. Compound s with H-bond donor functionality were retained much less than in the other investigated high-performance liquid chromatography (HPLC) systems. This u nique selectivity can be explained by the stronger adsorption of trifluoroe thanol on the perfluorinated stationary phase surface, than on the hydrocar bon surface. It suggests the importance of the adsorbed organic modifiers i n the separation mechanism during reversed-phase HPLC. (C) 2001 Elsevier Sc ience B.V. All rights reserved.