Enantiomeric separations on cyclodextrin-based and synthetic polymeric chiral stationary phases by high performance liquid chromatography and supercritical fluid chromatography

Abstract

High performance liquid chromatography (HPLC) employing chiral stationary phases (CSPs) is the most popular and effective method for the separation of enantiomers. In this dissertation, the first chapter is an overview of chiral stationary phases for HPLC, which includes the structures, separation mechanisms, and applications of a variety of chiral stationary phases. The use of some chiral stationary phases in SFC also is discussed. The next three chapters present the enantiomeric separations of chiral furans, isochromenes, and polycycles on cyclodextrin-based chiral stationary phases. The performance of chiral stationary phases for the separation of these analytes was compared. The effect of the mobile phase compositions and structures of the analytes on the chiral recognitions were discussed. Chapter 5 through chapter 7 focuses mainly on the development and evaluation of new synthetic polymeric chiral stationary phases. First, the enantiomeric separation abilities of a new polymeric chiral stationary phase based on the monomer N,N’-(1S,2S)-1,2cyclohexanediyl-bis-2-propenamide was screened with 200 racemic samples. The enantiomeric separations obtained were optimized. The mobile phase compositions and a mobile phase additive (trifluoroacetic acid) were evaluated and the chiral recognition mechanism was discussed. The new CSP showed high sample loading capacity. Then, we developed two new synthetic polymeric CSPs with two other monomers, which are polymerible derivatives of trans-1,2-diphenylethylenediamine and trans-9,10-dihydro-9,10ethanoanthracene-(11S,12S)-11,12-dicarboxylic acid. The two new CSPs also showed enantiomeric selectivities for a variety of chiral compounds and high sample loading capacity. The three new synthetic polymeric CSPs are complementary to each other. Chapter 8 is a study on the use of the new synthetic polymeric CSPs with supercritical fluid eluents. The new CSPs also can separate many compounds using supercritical fluid chromatography (SFC). They showed high stabilities under SFC conditions. Compared with HPLC, SFC provides much faster separations due to the high flow rates. For some analytes, better enantiomeric separations were observed with SFC due to the better separation efficiencies.