title: Comparison of liquid and supercritical fluid chromatography mobile phases for enantioselective separations on polysaccharide stationary phases.
abstract: Analysis and production of enantiomerically pure compounds is a major topic of interest when active pharmaceutical ingredients are concerned. Enantioselective chromatography has become a favourite both at the analytical and preparative scales. High-performance liquid chromatography (HPLC) and supercritical fluid chromatography (SFC) are dominating the scene and are often seen as complementary techniques. Nowadays, for economic and ecologic reasons, SFC may be preferred over normal-phase HPLC (NPLC) as it allows significant reductions in solvent consumption. However, the transfer of NPLC methods to SFC is not always straightforward. In this study, we compare the retention of achiral molecules and separation of enantiomers under supercritical fluid (carbon dioxide with ethanol or isopropanol) and liquid normal-phase (heptane with ethanol or isopropanol) elution modes with polysaccharide stationary phases in order to explore the differences between the retention and enantioseparation properties between the two modes. Chemometric methods (namely quantitative structure-retention relationships and discriminant analysis) are employed to compare the results obtained on a large set of analytes (171 achiral probes and 97 racemates) and gain some understanding on the retention and separation mechanisms. The results indicate that, contrary to popular belief, carbon dioxide - solvent SFC mobile phases are often weaker eluents than liquid mobile phases. It appears that SFC and NPLC elution modes provide different retention mechanisms. While some enantioseparations are unaffected, facilitating the transfer between the two elution modes, other enantioseparations may be drastically different due to different types and strength of interactions contributing to enantioselectivity.
authors.affiliation: ICOA, (1) CNRS UMR 7311 (2) Université d'Orléans, Pôle de Chimie, UFR Sciences - BP 6759, 45067 Orléans cedex 2, France.
authors.forename: Syame
authors.initials: S
authors.lastname: Khater
authors.affiliation: Novartis Institutes for BioMedical Research, WKL-122.P.25, 4002 Basel, Switzerland.
authors.forename: Marie-Anne
authors.initials: MA
authors.lastname: Lozac'h
authors.affiliation: Novartis Institutes for BioMedical Research, WKL-122.P.25, 4002 Basel, Switzerland.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Adam
authors.affiliation: Novartis Institutes for BioMedical Research, WKL-122.P.25, 4002 Basel, Switzerland.
authors.forename: Eric
authors.initials: E
authors.lastname: Francotte
authors.affiliation: ICOA, (1) CNRS UMR 7311 (2) Université d'Orléans, Pôle de Chimie, UFR Sciences - BP 6759, 45067 Orléans cedex 2, France. Electronic address: caroline.west@univ-orleans.fr.
authors.forename: Caroline
authors.initials: C
authors.lastname: West
mesh_terms: D002245:Carbon Dioxide / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D025924:Chromatography, Supercritical Fluid; D011134:Polysaccharides / Q000302:isolation & purification*; D012997:Solvents; D013237:Stereoisomerism
chemical_list: D011134:Polysaccharides; D012997:Solvents; D002245:Carbon Dioxide
keywords: Chemometrics; Enantiomer separation; Polysaccharide chiral stationary phase; Solvation parameter model; Supercritical fluid chromatography