Enantiomer separation of mandelates and their analogs on cyclodextrin derivative chiral stationary phases by capillary GC

Structure-Chiral Selectivity Relationships of Various Mandelic Acid Derivatives on Octakis 2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl-gamma-cyclodextrin Containing Gas Chromatographic Stationary

Frequently, a good chiral separation is the result of long trial and error processes. The three-point interaction mechanisms require the fair geometrical fitting and functional group compatibility of the interacting groups. Structure-chiral selectivity correlations are guidelines that can be established via trough systematic studies using model compounds. The enantiorecognition of the test compounds was studied on an octakis 2,3-Di-O-acetyl-6-O-tert-butyldimethylsilyl-gamma-cyclodextrin (TBDMSDAGCD) chiral selector. In our work, mandelic acid and its variously substituted compounds were used as model compounds to establish adaptable rules for other enantiomeric pairs. The mandelic acid and its modified compounds were altered at both their carboxyl and hydroxyl positions to test the key interaction forces of the chiral recognition processes. Ring- and alkyl-substituted mandelic acid derivatives were also used in our experiments. The chiral selectivity values of 20 test compounds were measured and extrapolated to 100 °C. The hydrogen donor abilities of test compounds improved their chiral selectivities. The inclusion phenomenon also played a role in chiral recognition processes in several cases. Enantiomer elution reversals were observed for different derivatives of hydroxyl groups, providing evidence for the multimodal character of the selector. The results of our research can serve as guidelines to achieve appropriate chiral separation for other enantiomeric pairs.

A novel chiral GC/MS method for the analysis of fluoxetine and norfluoxetine enantiomers in biological fluids

Aims:

A novel robust chiral gas chromatographic/mass spectrometric (GC/MS) method for the separation and measurement of fluoxetine and norfluoxetine enantiomers in urine and plasma was developed.

Materials and Methods:

The drug was extracted from the samples by a liquid–liquid technique, using chloroform, and the enantiomers were separated and measured on a chiral gas chromatographic column (HYDRODEX β-6TBDM^®, 0.25 μm × 0.25 mm × 50 m). GC/MS instrumentation was used for the acquisition of data in the electron impact selective-ion monitoring mode.

Results:

The ions chosen were of a mass-to-charge ratio (m/z) exactly equal to 44 units, in order to measure fluoxetine enantiomers, 134 units in order to measure norfluoxetine enantiomers, and 58 units in order to measure diphenhydramine, the internal standard. The method was found to be linear and reproducible in the 50–500 ng/mL concentration range for both urine samples and plasma samples and for both fluoxetine and norfluoxetine, with correlation coefficients ranging between 0.994 and 0.997.

Conclusions:

This methodology has an enormous potential for application in pharmacokinetic studies of the enantiomers of fluoxetine

Biotechnological applications of cyclodextrins

Cyclodextrins (CDs) are a family of cyclic oligosaccharides that are composed of alpha-1,4-linked glucopyranose subunits. Cyclodextrins are produced from starch by enzymatic degradation. These macrocyclic carbohydrates with apolar internal cavities can form complexes with and solubilize many normally water-insoluble compounds. This review describes recent applications of CDs in pharmaceuticals with a major emphasis on drug delivery systems. The utility of these water-soluble cyclic glucans in a variety of foods, flavors cosmetics, packaging and textiles is elaborated. The role of these compounds in biocatalysis is also discussed. Cyclodextrins are used in separation science because they have been shown to discriminate between positional isomers, functional groups, homologues and enantiomers. This property makes them a useful agent for a wide variety of separations.