Extending the scope of enantiomer separation by capillary supercritical fluid chromatography on immobilized polysiloxane-anchored permethyl-β-cyclodextrin (Chirasil-Dex)

Bioanalytical applications using supercritical fluid techniques

The bioanalytical applications of supercritical fluid techniques, such as supercritical fluid extraction (SFE) and supercritical fluid chromatography (SFC), are of increasing interest. The main role of these techniques is in the sample preparation and separation of biologically active compounds, particularly drugs and their metabolites, as well as endogenous compounds. An insight is given into the different types of extracting fluids and modifiers, detectors, stationary phases, mobile phases and collection strategies. A critical discussion is presented on the existing state of the art concerning the applications of SFC and SFE with a specific focus on its advantages and limitations in the bioanalytical field. New developments and the possibilities for routine work in the near future are also covered.

Enantioseparation on mono(6A-N-allylamino-6A-deoxy)permethylated β-cyclodextrin covalently bonded silica gel

A chiral selector, mono(6A-N-allylamino-6A-deoxy)permethylated beta-cyclodextrin, was synthesized through a facile synthetic route and chemically immobilized onto porous silica gel via hydrosilylation to afford a cyclodextrin based chiral stationary phase MeCD-CSP. This chiral stationary phase exhibited good enantioselectivity under standard HPLC conditions. The optimal resolution of 1-(p-bromophenyl)ethanol and bromopheniramine was achieved under normal-phase conditions using a mobile phase comprising n-hexane (hexane) and 2-propanol (IPA). The enantioseparation of warfarin, suprofen and a series of flavanones under reversed-phase conditions were optimized and efficient enantioseparations for these analytes were obtained.

Recent Advances in the Analysis of Steroid Hormones and Related Drugs

The development during the last 15 years and the state-of-the-art in the analysis of bulk steroid hormone drugs and hormone-like structures and pharmaceutical formulations made thereof are summarized. Other steroids (sterols, bile acids, cardiac glycosides, vitamins D) as well as biological-clinical aspects and pharmacokinetic and metabolic studies are excluded from this review. The state-of-the-art is summarized based on comparisons of monographs in the latest editions of the European Pharmacopoeia, United States Pharmacopoeia and the Japanese Pharmacopoeia. This is followed by sections dealing with new developments in the methodology for the fields of spectroscopic and spectrophotometric, chromatographic, electrophoretic and hyphenated techniques as well electroanalytical methods. The review is terminated by two problem-oriented sections: examples on impurity and degradation profiling as well as enantiomeric analysis.

Chiral separation by chromatographic and electromigration techniques. A review

This review gives a survey of different chiral separation principles and their use in high-performance liquid chromatography (HPLC), gas chromatography (GC), supercritical fluid chromatography (SFC), thin-layer chromatography (TLC), capillary electrophoresis (CE) and capillary electrochromatography (CEC) highlighting new developments and innovative techniques. The mechanisms of the different separation principles are briefly discussed and some selected applications are shown.

Gas chromatographic enantiomer separation of C-3 and C-4 synthons: prediction of absolute configuration from elution order and enzymatic resolution

Enantiomers of C-3 secondary alcohols, 3-hydroxybutanoates, and cyclic 1,3-dithioacetals were separated by chiral GLC using CP-Chirasil-Dex CB and Chiraldex G-TA columns. The former was most successful for analysis of n-alkyl esters of secondary alcohols and the separation depended on the chain length of the acyl group and the electronic and steric properties of the other substituents. The Chiraldex G-TA column was efficient for analysis of secondary alcohols, derivatized as their trifluoroacetates. The elution order of the secondary alcohols and the corresponding acetates was always the same with respect to the size of groups connected to the stereocenter. However, when the secondary alcohols were analyzed as their trimethylsilyl derivatives, the elution order was reversed. Elution order on chiral columns and enantiomeric ratios, E-values, obtained in kinetic resolutions catalyzed by lipase B from Candida antarctica (CALB) were evaluated as a method for prediction of absolute configuration. The usefulness of the method was demonstrated using 22 pairs of enantiomers. Copyright 1999 Wiley-Liss, Inc.

Unified enantioselective capillary chromatography on a Chirasil-DEX stationary phase. Advantages of column miniaturization

Immobilized Chirasil-DEX (mono-6-O-octamethylenepermethyl-beta-cyclodextrin chemically linked to dimethylpolysiloxane) can be employed as a versatile chiral stationary phase in chromatography. The chiral polymer has a long lifetime and is configurationally and thermally stable. The concept of unified enantioselective chromatography has been demonstrated for the enantiomer separation of hexobarbital by gas chromatography, supercritical fluid chromatography, liquid chromatography and capillary electrochromatography on a single open-tubular column (1 m x 50 microns I.D.) coated with Chirasil-DEX. The advantages of miniaturization in contemporary chromatographic enantiomer separation are demonstrated. Chirasil-DEX coated on porous silica is also useful for enantiomer separation in high-performance liquid chromatography.