Thomas E. Beesley

The present state-of-the-art in chiral capillary gas chromatography (GC) is reviewed in this article. The article provide a short historical overview of phase development followed by a comparison of GC and high performance liquid chromatography (HPLC) chiral separations. After a short discussion of mechanisms of the most popular cyclodextrin phases...

The development of chiral column technology since the review in 2008 is discussed by Thomas Beesley, a pioneer in the chromatographic separations of enantiomeric compounds. He discusses the use of generic chiral stationary phase (CSP) screening to find the optimum column, the use of smaller diameter columns for high performance liquid chromatograph...

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Development of chiral separations has been essential to the drug discovery and development process. The solubility requirements for a number of methods and/or the mobile phase requirements for application of certain detection systems have opened up many opportunities for cyclodextrin-based CSPs for liquid chromatography. Even though a few chiral st...

Obtaining enantioselective separations using bonded macrocyclic glycopeptides has increased dramatically over the last several years. The products, trademarked CHIROBIOTIC phases, have advanced based on a host of publications shedding light on the mechanisms of interaction for a variety of diverse chiral analytes. This presentation will cover a bri...

IntroductionStructural Characteristics of Macrocyclic Glycopeptide CSPs Chiral Recognition MechanismsMulti-modal Chiral Stationary PhasesEnantioselectivity as a Function of Molecular Recognition Ionizable Molecules Polar Ionic ModeReversed-phase ModeNeutral MoleculesComplementary EffectsMethod DevelopmentOptimization Procedures Polar Ionic ModeReve...

A new synthetic polymeric chiral stationary phase for liquid chromatography was prepared via free-radical-initiated polymerization of trans-9,10-dihydro-9,10-ethanoanthracene-(11S,12S)-11,12-dicarboxylic acid bis-4-vinylphenylamide. The new polymeric chiral stationary phase (CSP) showed enantioselectivity for many chiral compounds in multiple mobil...

The comparisons of five different chiral stationary phases (CSPs) based on 2,6-dinitro-4-trifluoromethylphenyl (DNP-TFM) ether substituted β-cyclodextrin are presented. The five CSPs differ from each other in the linkage/spacer chemistry, or on the position of the substituents on β-cyclodextrin, or in the sequence of the synthetic procedure. The re...

The synthesis and evaluation of new dinitrophenyl (DNP) substituted beta-cyclodextrin (beta-CD) chiral stationary phases (CSPs) for the enantioseparation of various classes of chiral analytes by HPLC are presented. The dinitrophenyl substituted beta-CD derivatives are synthesized and covalently bonded to functionalized 5 microm spherical porous sil...

Chiral separations remain high on the priority list of drug developers. Liquid chromatography and supercritical fluid chromatography continue to vie for dominance in the chiral separation market but might be reaching the state of complementary methodologies. New separation technologies and new advances in current products continue to elevate the st...

A synthetic polymeric chiral stationary phase for liquid chromatography based on N, N′-[(1R,2R)-1,2-diphenyl-1,2-ethanediyl]bis-2-propenamide monomer was prepared via a simple solution initiated radical polymerization. This stable chiral stationary phase showed enantioselectivities for a large number of racemates in polar organic and normal phase m...

This new dinitrophenyl derivative of the CYCLOBOND cyclodextrin technology is a highly stable π electron sharing system bonded through an ether linkage that has shown remarkable stability and greater selectivity than any other derivative of cyclodextrins tested.

Enantiomeric gas chromatography (GC) has demonstrated the potential for a broad array of applications in diverse industries; it remains a dynamic area for analytical chiral separations. This article reviews original research papers published in the period from 2001 to present, dealing with the applications of chiral GC for direct enantiomeric separ...

Chiral stationary phases (CSPs) based on polymeric (R,R)- or (S,S)-1,2-diaminocyclohexane (DACH) derivatives are synthesized. When bonded to 5 microm porous spherical silica gel, the poly (trans-1,2-cyclohexanediyl-bis acrylamide) based poly-cyclic amine polymer (P-CAP) stationary phases is proved to be effective chiral stationary phases that could...

Seventy-one chiral compounds were separated on four macrocyclic glycopeptide chiral selectors: teicoplanin, its aglycone, ristocetin A and vancomycin, using three possible separation modes: reversed phase with methanol/buffer mobile phases, normal phase with hexane/ethanol mobile phases and polar ionic mode (PIM) with 100% methanol mobile phase wit...

Fritless particle-loaded monoliths for chiral capillary electrochromatographic (CEC) separation were prepared. Silica particles containing a chiral selector are suspended in a monomer solution, which is drawn into the capillary followed by in situ polymerization. Thereby the silica-based particles containing the chiral selector are embedded in a no...

A large increase in sample capacity and resolution has been observed when the linkage length and position is altered when bonding vancomycin to silica gel. The resulting CHIROBIOTIC V2 chiral stationary phase demonstrates improved separations in the polar organic and polar ionic

IntroductionCharacteristics of macrocyclic glycopeptide CSPs Chiral recognition mechanismsMulti-modal CSPsPredictability of enantioselectivityComplementary separationsMethod development with glycopeptide CSPs Method development protocolsColumn coupling techniqueOptimization Effect of flow rate and temperature on enantiomeric separationsOptimization...

Given the increasing number of chiral samples and the time constraints under which chromatographers work, choosing an appropriate chiral stationary phase for the resolution of enantiomers can be challenging. In this article, the authors describe a screening approach for chiral HPLC method development. They used three 10 cm × 0.46 cm columns packed...

The effects of solvent composition and temperature on the retention and resolution of the (S)- and (R)- enantiomers of 4-benzyl-2-oxazolidinone are reported. The data obtained is used to assess the effect of solvent composition and temperature on the efficiency required to effect the separation, the minimum variance per unit length of the column, t...

The enantioselectivity of native β-cyclodextrin and its 2,3-methylated analogue were examined in both the “polar-organic” mode and the reversed phase mode. By comparing these two chiral selectors, the function of the secondary 2,3-hydroxyl groups at the mouth of the cyclodextrin can be examined (in regard to selectivity and retention). In the “pola...

Both β-cyclodextrin and 2,3-methylated-β-cyclodextrin bonded stationary phases effectively separate a variety of structural and geometrical isomeric compounds in the reversed phase mode. The retention of neutral structural isomeric compounds, as well as substituted phenols and anilines, was usually longer on the methylated cyclodextrin stationary p...

Enantiomeric separation of amphetamine and methamphetamine as achiral derivatives on 2,6-di-O-pentyl-3-O-trifluoroacetyl--cyclodextrin, 2,6-di-O-pentyl-3-O-trifluoroacetyl--cyclodextrin and 2,6-di-O-pentyl-3-O-propionyl--cyclodextrin stationary phase in capillary gas chromatography is described. Trifluoroacetic anhydride and acetic anhydride were u...

Many active drugs are racemic mixtures. Because the two enantiomers of a racemate often cause different pharmacological responses, the use of optically pure isomers is desirable and may be soon required. Cyclodextrin-bonded silica gel can be used as chiral stationary phase (CSP) in liquid chromatography. The enantiomers of 25 different racemic drug...

Inclusion complexes formed with substituted aromatic compounds and ß-cyclodextrin were studied using molecular modeling techniques. Energies of the MM2 optimized structures were correlated with HPLC retention times. A direct correlation between the inclusion complex stability and the HPLC retention times for the bonded ß-cyclodextrin was found with...

The effect of column dimension on resolution, sample capacity, retention time, efficiency and mobile phase composition were studied, using both constant flow rate and constant linear velocity. The four columns selected (A = 238 × 3.2 mm, B = 153 × 4.0 mm, C = 116 × 4.6 mm and D = 50 × 7 mm) had the same volume. K values were found to be constant, w...

A study of mixed C18/β packings in high performance liquid chromatography was undertaken to evaluate the utility of such phases. The results show that non additive retention times are obtained when a mixed phase column is used while the retention times are additive when two columns, one packed with C18 and the other with β are coupled in a series....

For many drugs, only racemic mixtures are available for clinical use. Because different stereoisomers of drugs often cause different physiological responses, the use of pure isomers could elicit more exact therapeutic effects. Differential complexation of a variety of drug stereoisomers by immobilized beta-cyclodextrin was investigated. Chiral reco...

The basic steps of the thin layer chromatographic process are described with a brief introduction to instrumentation that is currently available to increase sample throughput and enhance sensitivity, reproducibility, and reliability. Tables listing suppliers, applicable devices, processing costs, and sensitivity are included. Photographs of the var...

Two-dimensional/2D/ chromatography was first described by Kirchner in 1951. A sample applied to one corner of a 20 × 20cm plate approximately 1.5cm from each edge is developed in a mobile phase that resolves the polar constituents. It is then dried, rotated 90 degrees to the first direction and placed in a second mobile phase designed to resolve th...

A simple method of quantitatively determining C-18 fatty acids in an aqueous oxidized polyethylene emulsion is presented, utilizing the formation of phenacyl esters in the presence of crown ether as catalyst, followed by separation by reversed-phase thin layer chromatography, and subsequent densitometry of the strongly ultraviolet absorbing separat...

The successful use of N-carboxy-α-amino acid anhydrides (NCA's) in the controlled synthesis of optically pure dipeptides in aqueous medium is described. High yields of dipeptides were obtained by adding the crystalline NCA directly to an aqueous solution of an amino acid at 0-2° and generally at pH 10.2 with rapid mixing of reactants, thus minimizi...

One of the three pigments isolated in crystalline form from the mycelium of the dermatophyte, Trichophyton rubrum, has been shown to be identical with the pigment, xanthomegnin, previously isolated from T. megnini. Several additional derivatives of the compound are reported.

The Journal of Investigative Dermatology publishes basic and clinical research in cutaneous biology and skin disease.