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| Author | : Weiyong Li |
| Publisher | : |
| Total Pages | : 138 |
| Release | : 1991 |
| Genre | : |
| ISBN | : |
| Author | : |
| Publisher | : |
| Total Pages | : |
| Release | : 2004 |
| Genre | : Cyclodextrins |
| ISBN | : 9789741761289 |
Eanatiomeric separations of aromatic epoxides were studied by means of capillary gas chromatography using heptakis(2,3,di-O-methyl-6-O-tert-butyldi methylisilyl)cyclomaltoheptaose (or BSiMe) and heptakis(2,3-di-O-acetyl-6-O-tert-butyldimethylsiloyl)cyclomaltoheptaose (or BSiAc) as chiral stationary phases. The effects of substitution types and position of styrene oxide derivatives on retention and enantioselectivity have been investigated. Thermodynamic data on the interaction of enantiomers with chiral stationary phases were collected in detail in order to clarify the strength of analyte-stationary phase interaction and enantioselectivity towards the selected groups of epoxides. All eposides with different substitution type and position were successfully separated with either BSiMe or BSiAc, or otherwise both of them. On both columns, the number, type, and position of analyte substitution have a strong influence on enantioselectivity. The type of substituent on cyclodextrin molecule (BSiMe vs.BSiAc) also affect enatioselectivity of epoxides greatly. Both columns can be used to compliment one another as their resolving abilities are quite opposite.
| Author | : Pattama Changseeplag |
| Publisher | : |
| Total Pages | : 238 |
| Release | : 2002 |
| Genre | : Cyclodextrins |
| ISBN | : 9789741718962 |
Enantiomeric separations of some esters were studied by means of capillary gas chromatography using heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl) cyclomaltoheptaose (or BSiMe) and heptakis(2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl)cyclomaltoheptaose (or BSiAc) as stationary phases. The influence of analyte structure, e.g. the type and position of substituent together with ester chain length, on retention and enantioselectivity was systematically investigated. Thermodynamic data were also calculated in order to clarify the strength of analyte-stationary phase interaction and enantioselectivity towards these selected groups of esters. All esters with different substitution patterns were successfully separated with either BSiMe or BSiAc, or otherwise both of them. Generally, BSiAc phase exhibited greater enantioselectivity towards most analytes than BSiMe phase. From chromatographic and thermodynamic data obtained, it can be concluded that the structure of ester analytes plays an important role on separation. In most cases, the interaction of these two phases towards esters slightly increased with lengthening alkyl chain while enantioselectivity significantly decreased. Also, changing the position of substituent or chiral center caused changes in the interaction and enantioselectivity. Moreover, the degrees of interaction strength and sites as well as enantioselectivity of these esters depended upon the size and polarity of substituents.
| Author | : Weihua Tang |
| Publisher | : Springer Science & Business Media |
| Total Pages | : 266 |
| Release | : 2013-05-24 |
| Genre | : Science |
| ISBN | : 3642376487 |
Modified Cyclodextrins for Chiral Separation offers a review of the latest advances in developing modified cyclodextrins as chiral selectors for various chromatographic and electromigration techniques. Over the years, many descriptions of chiral separation have appeared in academic journals and books, but most of them have been devoted to either the development of analytical methods and protocols or the summary of different chiral selectors, including cyclodextrins for chiral separation applications. This is in marked contrast to this volume which focuses on the research endeavors concerning the development of cyclodextrin derivatives specifically as either chiral mobile phases for capillary electrophoresis, or chiral stationary phases for various chromatographic techniques including gas chromatography, or high-performance liquid chromatography and supercritical fluid chromatography. The ongoing thread in this book is the synthesis of structurally-defined cyclodextrin derivatives and their applications in enantiomer separation by means of different analytical techniques. Modified Cyclodextrins for Chiral Separation is intended for those who are interested in expanding their knowledge of cyclodextrin chemistry and chiral separation, and in what cyclodextrin modification can be made to suit the needs of chiral selectors for different analytical techniques. It primarily focuses on the state-of-the-art cyclodextrin chemistry which is the basis for all chiral selectors used in these chiral separation techniques. Weihua Tang, PhD, is a professor at the Key Laboratory of Soft Chemistry and Functional Materials, Ministry of Education, Nanjing University of Science and Technology, China. Siu-Choon Ng, PhD, is a professor at the Division of Chemical and Biomedical Engineering, School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore. Dongping Sun, PhD, is a professor at the Key Laboratory of Soft Chemistry and Functional Materials, Ministry of Education, Nanjing University of Science and Technology, China.
| Author | : Thomas E. Beesley |
| Publisher | : John Wiley & Sons |
| Total Pages | : 526 |
| Release | : 1999-01-26 |
| Genre | : Science |
| ISBN | : 9780471974277 |
Eine Ergänzung anderer, in der Reihe Separation Sciences bereits erschienener Titel. Viel Theorie und zahlreiche Anwendungsbeispiele für die Praxis der chiralen HPLC- und GC-Trennung machen dieses top-aktuelle Buch zu einer unverzichtbaren Informationsquelle für jeden Neueinsteiger auf diesem Gebiet. (11/98)
| Author | : Wilfried A. König |
| Publisher | : |
| Total Pages | : 184 |
| Release | : 1992 |
| Genre | : Science |
| ISBN | : |
| Author | : |
| Publisher | : |
| Total Pages | : 224 |
| Release | : 2006 |
| Genre | : Cyclodextrins |
| ISBN | : |
Enantiomeric separations of 90 alcohols were studied by means of capillary gas chromatography using hexakis (2,3-di-O-methyl-6-O-tert-butyldimethylisilyl)cyclo-maltohexaose (or ASiMe) as chiral stationary phase. The influence of type, position and number of substituent, position of chiral center, and main-structure of alcohols, on retention and enantioselectivity was systematically investigated. Thermodynamic data and molecular docking calculation were also acquired to clarify the strength of analyte-stationary phase interaction and the mechanism of chiral recognition towards the selected groups of alcohols. The gas chromatographic results indicated that all tested analytes, except for 12,15,17, 4OMe, 4OMeBen and 2but, could be successfully enantioseparated with ASiMe. Among 90 alcohols studied, the best enantioseparation was observed on 1-(2,5-difluorophenyl)-ethanol. The effect of position of substituent towards enantioseparation was clearly seen from mono-substituted 1-phenylethanols. The enantioseparation increased as the position of substituent was in the order of para-
| Author | : |
| Publisher | : |
| Total Pages | : |
| Release | : 2002 |
| Genre | : |
| ISBN | : |
Cyclodextrin (CD) derivatives are widely used as chiral stationary phases in capillary gas chromatography. Their performance depends substantially on the side chains attached to the hydroxyl groups of the glucose moieties. In this study new classes of CD-derivatives suitable for gas chromatographic (GC) separation of enantiomers were synthesized by introducing (i) acetal functions and (ii) chiral acyl moieties at positions 2 and 3 of the glucose units. Octakis(2,3-di-O-methoxymethyl-6-O-tert-butyldimethylsilyl)-g-cyclodextrin (2,3- MOM-6-TBDMS-g-CD) obtained by reaction of 6-O-TBDMS-g-cyclodextrin with methoxymethylchloride (MOM-Cl) was synthesized as first representative of cyclodextrin GC stationary phases containing alkoxymethyl side chains. The structure was confirmed by NMR and mass spectrometry. The suitability of the material diluted in polysiloxane as GC stationary phase was shown. Enantioseparations could be achieved for a broad spectrum of chiral volatiles from various chemical classes. Structural influences of the analytes on the enantiodifferentiations were demonstrated. High separation factors were observed for the hydroxyketone acetoin (a = 1.8) and some methyl branched ketones. Pronounced enantioseparations were also determined for cyclic pentenolone and furanone derivatives. To investigate the impact of the size of the CD torus, the 2,3-MOM-derivatives of the b- and a-CD analogs were synthesized. The spectrum of compounds for which enantiomers could be separated on 2,3-MOM-6-TBDMS-b-CD was more limited and the enantioseparations achieved were generally less pronounced compared to the g-CD derivative. However, for 2-alkyl esters unusually high separation factors (a up to 4.31) were observed. Using 2-pentyl acetate as example, phenomena underlying the enantioseparation were investigated by determining thermodynamic parameters. The data showed that only one enantiomer is retained significantly on the chiral stationary phase whereas the other one behaves.
| Author | : D. Stevenson |
| Publisher | : Springer Science & Business Media |
| Total Pages | : 203 |
| Release | : 2012-12-06 |
| Genre | : Science |
| ISBN | : 1461566347 |
This volume represents the proceedings of a two-day international meeting on chiral chromatography held at the University of Surrey between 3-4 September 1987. The meeting was jointly organized by the Chromatographic SOCiety and the Robens Institute of the University of Surrey in response to the burgeoning interest in this rapid maturing field of chromatography. Nowhere is this interest more evident than in the agrochemical and pharmaceutical industries where the implications of different pharmacological and toxicological activity for the individual enantiomers present in a racemic drug ol" insecticide is an increasing area of concern. Developments in the area of chiral separations are at last beginning to provide SCientists with the necessary tools to study how animals and man handle racemates and relate their obseIVations to the obseIVed biological effects of these substances. The development of robust and Simple methods for the separation of enantiomers will therefore have a profound Impact on safety evaluation and drug design. The meeting proved to be very successful. with over 160 delegates from thirteen countries in Europe and America present to learn from the experiences of experts in the field of chiral chromatography and to hear about the latest developments. Hopefully. in future symposia on chiral separations at the University of Surrey.
| Author | : Wilfried A. König |
| Publisher | : |
| Total Pages | : 128 |
| Release | : 1987 |
| Genre | : Chirality |
| ISBN | : |
