Cyclodextrin-modified solvent extraction for polynuclear aromatic hydrocarbons

The extraction efficiencies of several polynuclear aromatic hydrocarbons (PAHs) between Isopropyl ether/water and between Isopropyl ether: 1-butanol (1:4)/water are measured in the presence of an aqueous γ-cyclodextrin (CDx) modifier at room temperature. The distribution of certain PAHs Into the aqueous phase is Increased by the presence of 10-2M γ -cdx. For compounds such as perylene and coronene, which show the most marked effects, the extraction efficiencies Into the aqueous phase from pure Isopropyl ether are 95.1% and 93.7%, respectively, when the CDx modifier Is used. In the mixed solvent system with 1-butanol, these values are 63.4% and 98.1 %, respectively. In both systems, the Increased distribution into water is based in part on the size relationship between the PAH and the CDx cavity. In the case of relatively small molecules like anthracene, little or no extraction Is observed in the presence of the CDx modifier. This type of extraction system may be useful for selective extraction of large PAHs from mixtures. Extraction results for a variety of PAHs are presented and discussed. © 1988, American Chemical Society. All rights reserved

Determination of cyclodextrin formation constants using dynamic coupled-column liquid chromatography

Dynamic coupled-column liquid chromatography is used to determine both aqueous solubilities and cyclodextrin inclusion complex formation constants for a series of polynuclear aromatic hydrocarbons (PAHs). This method Is based on the increase In solubility afforded by cyclodextrlns upon complexation. Formation constant (Kf) values are determined by using α-, β-, and γ-cyclodextrlns at various temperatures. The relative precision of the calculated Kf values is best for cyclodextrin/PAH complexes with large formation constants. The calculated solubilities are comparable to literature values, and in most cases, formation constant data are reproducible within 10%. The resulting Kf values confirm that the formation of Inclusion complexes is based on the relative sizes of host and guest molecules. © 1989, American Chemical Society. All rights reserved

Enantiomeric resolution and chiral recognition of racemic nicotine and nicotine analogs by .beta.-cyclodextrin complexation. Structure-enantiomeric resolution relationships in host-guest interactions

High-performance liquid chromatography using β-cyclodextrin bonded phases was examined for the enantiomeric separation of racemic nicotine and 19 racemic nicotine analogues. Ten pairs of enantiomers were separated by this technique. This represents the first reported facile and direct separation of these racemates. Effects of pH, mobile phase composition, and structural features of the substrates (i.e., position and size of substituents, presence of pyrrolidine ring or hydrogen bonding functionalities, basicity) on the enantioselectivity are examined. Various structural aspects of the compounds were related to retention to the cyclodextrln-modlfied support and to the enantiomeric separations observed. Implications of this work to host-guest complexation are discussed. © 1988, American Chemical Society. All rights reserved