Effect of identity and number of chiral microemulsion components in chiral microemulsion electrokinetic chromatography.

摘要

The field of microemulsion electrokinetic chromatography (MEEKC) is one of the newer subsets of electrokinetic chromatography (EKC) in which microemulsion droplets (consisting of three components: surfactant, cosurfactant, and oil) aid in analyte separation. The benefits to utilizing this methodology include short analysis times, high efficiencies, multiple parameters to fine-tune, ability to solubilize hydrophobic compounds, and minute consumption of both mobile phase and sample. This research area continues to expand as additional microemulsion formulations are examined for the analysis of more diverse and complex samples. In particular, the composition of the nanodroplets has a major impact on the separation characteristics. Therefore, the effect of each individual microemulsion constituent depends on the identity of the other components. It was the aim of this work to examine the impact of cosurfactant and oil identity and stereochemistry in dodecoxycarbonylvaline (DDCV)-based chiral microemulsion formulations for chiral MEEKC.; In Chapter 3, the preparation of novel dual-chirality microemulsions is described wherein the chiral surfactant DDCV, in each of its stereochemical configurations, is combined with the chiral cosurfactant S-2-hexanol for the separation of two pairs of enantiomers. Additionally, results with racemic 2-hexanol were obtained and compared to previously published data using 1-butanol as the cosurfactant.; The focus of Chapter 4 is the effect of achiral cosurfactant identity in which seven different achiral alcohols are examined for their influence on chromatographic figures of merit. Both the alkyl chain length and the hydroxyl group position caused distinct changes in the separation characteristics.; Chapters 5 through 7 describe several novel multi-chirality microemulsion formulations. Combinations of a chiral surfactant (DDCV) and a chiral oil are evaluated with two different chiral oils: dibutyl tartrate in Chapter 5 and diethyl tartrate in Chapter 6. Finally, in Chapter 7, novel triple-chirality microemulsions containing DDCV, S-2-hexanol, and diethyl tartrate are used for the analysis of six pairs of chiral enantiomers.; The findings of these studies demonstrate that both the identity and stereochemistry of the individual microemulsion components affect efficiency, enantioselectivity, and resolution. Importantly, the incorporation of additional chiral reagents to a microemulsion formulation provides a unique method of improving chiral separations.