The Experts below are selected from a list of 207 Experts worldwide ranked by ideXlab platform

Georges Guiochon - One of the best experts on this subject based on the ideXlab platform.

  • Csaba Horváth and Preparative Liquid Chromatography.
    Journal of chromatography. A, 2005
    Co-Authors: Georges Guiochon
    Abstract:

    Few chromatographers have been interested in furthering Preparative Liquid Chromatography. The pioneers, Tswett, Kuhn and Lederer, A.J.P. Martin, Tiselius, isolated fractions but as an intermediate step in the analysis of their samples. The progress in electronics and sensors, and in their miniaturization has lead to the paradoxical situation that the analysts never see the transient pure fractions that their detector quantitates. Yet, over the last 25 years, Preparative Liquid Chromatography has become an important industrial process for the separation, the extraction, and/or the purification of many pharmaceuticals or pharmaceutical intermediates, including pure enantiomers, purified peptides and proteins, compounds that are manufactured at the relatively large industrial scale of a few kilograms to several hundred tons per year. This development that has strongly affected the modem pharmaceutical industry is mainly due to the pioneering work of Csaba Horváth. His work in Preparative HPLC was critical at both the practical and the theoretical levels. He was the first scientist in modem times to pay serious attention to the relationships between the curvature of the equilibrium isotherms, the competitive nature of nonlinear isotherms, and the chromatographic band profiles of complex mixtures. The thermodynamics of multi-component phase equilibria and mass transfer kinetics in Chromatography attracted his interest and were the focus of ground-breaking contributions. He investigated displacement Chromatography, an old method invented by Tiselius that Csaba was first to implement in HPLC. This choice was explained by the essential characteristic of displacement Chromatography, in that it delivers fractions that can be far more concentrated than the feed. Remarkably, once the basics of nonlinear Chromatography had been mastered in his group, most of the applications that were studied by his coworkers dealt with peptides of various sizes and with proteins. Thus, all the applications of Preparative HPLC in the biotechnologies derive directly from Csaba's work. Although displacement did not pan out as a general method, the reasons are related more to practical constraints of the production of pharmaceuticals and to the long period of cheap energy that might be ending now. This report reviews Csaba's work in nonlinear Chromatography.

  • Preparative Liquid Chromatography.
    Journal of Chromatography A, 2002
    Co-Authors: Georges Guiochon
    Abstract:

    The status of the theory and the main methods of implementation of Preparative Liquid Chromatography are reviewed. On the theory front, the focus has recently shifted. The theory of non-linear, non-ideal Chromatography has given rise to numerous models whose advantages, disadvantages and ranges of application are now well understood. Interest now resides in investigating the equilibrium thermodynamics of complex new systems, in the study of the kinetics of mass transfers in conventional chromatographic systems, and in the application of the various models of Chromatography to optimize the experimental conditions. Progress in computer technology allows the use of sophisticated models, provided their parameters can be measured. This allows the detailed investigation of separations for which the mass transfer kinetics is slow such as chiral separations, the purification of basic compounds, and the extraction of recombinant proteins. On the applied front, in addition to numerous incremental improvements in reliability and economic performance, a few essential new features should be noted, i.e. the availability of instruments for simulated moving bed separations at the scale needed for Preparative chiral separations, the use of expanded beds for the extraction of recombinant proteins from fermentation broths, and the attention given to improvements in the performance of packed beds. A survey of the literature dealing with practical applications and recent meetings shows that Preparative Chromatography is becoming a well established separation and purification method in the pharmaceutical industry.

  • Preparative Liquid Chromatography a,b ,
    2002
    Co-Authors: Georges Guiochon
    Abstract:

    The status of the theory and the main methods of implementation of Preparative Liquid Chromatography are reviewed. On the theory front, the focus has recently shifted. The theory of non-linear, non-ideal Chromatography has given rise to numerous models whose advantages, disadvantages and ranges of application are now well understood. Interest now resides in investigating the equilibrium thermodynamics of complex new systems, in the study of the kinetics of mass transfers in conventional chromatographic systems, and in the application of the various models of Chromatography to optimize the experimental conditions. Progress in computer technology allows the use of sophisticated models, provided their parameters can be measured. This allows the detailed investigation of separations for which the mass transfer kinetics is slow such as chiral separations, the purification of basic compounds, and the extraction of recombinant proteins. On the applied front, in addition to numerous incremental improvements in reliability and economic performance, a few essential new features should be noted, i.e. the availability of instruments for simulated moving bed separations at the scale needed for Preparative chiral separations, the use of expanded beds for the extraction of recombinant proteins from fermentation broths, and the attention given to improvements in the performance of packed beds. A survey of the literature dealing with practical applications and recent meetings shows that Preparative Chromatography is becoming a well established separation and purification method in the pharmaceutical industry.  2002 Elsevier Science B.V. All rights reserved.

  • Comparing the optimum performance of the different modes of Preparative Liquid Chromatography
    Journal of chromatography. A, 1998
    Co-Authors: Attila Felinger, Georges Guiochon
    Abstract:

    A comparative study of the optimization of the different modes of the Preparative separation of binary mixtures by Liquid Chromatography is presented. Band profiles were calculated by means of the equilibrium-dispersive model of Chromatography in the cases of isocratic elution, gradient elution, and displacement Chromatography. The objective function to be maximized was the product of the production rate and the recovery yield. The production rate was calculated using the same definition of the cycle time in all cases. This common definition accounts for column regeneration after each run in each mode of the separation. The calculations reveal that the number of experimental parameters to be adjusted to achieve optimum separations is relatively small. The major parameters are the loading factor and the number of theoretical plates, besides the displacer concentration in displacement Chromatography, or the gradient steepness in gradient elution. The relative advantages of the different modes of Preparative Chromatography are discussed.

  • modeling of Preparative Liquid Chromatography
    Journal of Chromatography A, 1994
    Co-Authors: Georges Guiochon, Sadroddin Golshanshirazi
    Abstract:

    Abstract In order to achieve an acceptable production rate at reasonable cost, Preparative Chromatography must be carried out with phase systems in which the kinetics of mass transfers and adsorption—desorption are fast. Accordingly, band profiles in overloaded chromatographic columns are best understood by considering the ideal model, while the process itself is most suitably modeled using the equilibrium-dispersive model. The former model assumes an infinite column efficiency, while the latter lumps the contributions of axial dispersion and mass transfer resistances into a single apparent dispersion coefficient. The properties and solutions of these models are reviewed. The conditions under which they give satisfactory results are summarized. The excellent agreement between the experimental band profiles of the components of binary mixtures and the individual band profiles calculated with the equilibrium-dispersive model is demonstrated. The degree of agreement is limited only by the accuracy with which the competitive equilibrium isotherms are accounted for.

Yun Wei - One of the best experts on this subject based on the ideXlab platform.

  • Online isolation and purification of four phthalide compounds from Chuanxiong rhizoma using high-speed counter-current Chromatography coupled with semi-Preparative Liquid Chromatography
    Journal of chromatography. A, 2013
    Co-Authors: Yun Wei, Wenwen Huang
    Abstract:

    Abstract The phthalide compounds of Chuanxiong rhizoma including senkyunolide A, levistolide A, Z-ligustilide and 3-butylidenephthalide, have been reported as the biologically active compounds because of their therapeutic effects. In this work, online high-speed counter-current Chromatography coupled with semi-Preparative Liquid Chromatography instrument was set up, and online separation of the four compounds has been simultaneously achieved using this instrument. In this study, using all the selected solvent system, Z-ligustilide and 3-butylidenephthalide were eluted in one peak by high-speed counter-current Chromatography. Using high-speed counter-current Chromatography with a solvent system of n -hexane–ethyl acetate–methanol–water–acetonitrile (8:2:5:5:5, v/v), 3.6 mg of senkyunolide A (94.4%) and 3.0 mg of levistolide A (95.3%) were obtained from 100 mg of the crude extract. Coeluted Z-ligustilide and 3-butylidenephthalide peak fraction (8 mL) from high-speed counter-current Chromatography was directly transferred and injected to the semi-Preparative Liquid Chromatography for further separation. Finally, 5.6 mg of Z-ligustilide (97.5%) and 4.8 mg of 3-butylidenephthalide (99.3%) were obtained. The identification of these four compounds was performed by quadrupole time-of-flight mass spectrometer, 1 H and 13 C nuclear magnetic resonance spectrometer.

  • Preparative separation of gallic acid from chinese traditional medicine by high speed counter current Chromatography and followed by Preparative Liquid Chromatography
    Separation and Purification Technology, 2007
    Co-Authors: Yun Wei, Qipeng Yuan
    Abstract:

    Abstract The separation of active compounds from natural sources may encounter various problems, such as the compound of interest is of present only as a minor component in an extremely complex mixture. High-speed counter-current Chromatography (HSCCC) and Preparative Liquid Chromatography were used successively for isolation and purification of gallic acid from pomegranate husk. The two phase solvent system of HSCCC composed of ethyl acetate–methanol–water (50:1:50, v/v), which has been selected by analytical HSCCC. Using Preparative HSCCC and Preparative Liquid Chromatography, about a 500 mg amount of the crude extract was separated, yielding 15 mg of gallic acid at a high purity of over 96%.

Wenwen Huang - One of the best experts on this subject based on the ideXlab platform.

  • Online isolation and purification of four phthalide compounds from Chuanxiong rhizoma using high-speed counter-current Chromatography coupled with semi-Preparative Liquid Chromatography
    Journal of chromatography. A, 2013
    Co-Authors: Yun Wei, Wenwen Huang
    Abstract:

    Abstract The phthalide compounds of Chuanxiong rhizoma including senkyunolide A, levistolide A, Z-ligustilide and 3-butylidenephthalide, have been reported as the biologically active compounds because of their therapeutic effects. In this work, online high-speed counter-current Chromatography coupled with semi-Preparative Liquid Chromatography instrument was set up, and online separation of the four compounds has been simultaneously achieved using this instrument. In this study, using all the selected solvent system, Z-ligustilide and 3-butylidenephthalide were eluted in one peak by high-speed counter-current Chromatography. Using high-speed counter-current Chromatography with a solvent system of n -hexane–ethyl acetate–methanol–water–acetonitrile (8:2:5:5:5, v/v), 3.6 mg of senkyunolide A (94.4%) and 3.0 mg of levistolide A (95.3%) were obtained from 100 mg of the crude extract. Coeluted Z-ligustilide and 3-butylidenephthalide peak fraction (8 mL) from high-speed counter-current Chromatography was directly transferred and injected to the semi-Preparative Liquid Chromatography for further separation. Finally, 5.6 mg of Z-ligustilide (97.5%) and 4.8 mg of 3-butylidenephthalide (99.3%) were obtained. The identification of these four compounds was performed by quadrupole time-of-flight mass spectrometer, 1 H and 13 C nuclear magnetic resonance spectrometer.

Qipeng Yuan - One of the best experts on this subject based on the ideXlab platform.

Xiaohua Xiao - One of the best experts on this subject based on the ideXlab platform.

  • microwave assisted extraction coupled with counter current Chromatography and Preparative Liquid Chromatography for the preparation of six furocoumarins from angelica pubescentis radix
    Separation and Purification Technology, 2015
    Co-Authors: Gengjinsheng Cheng, Xiaohua Xiao
    Abstract:

    Abstract An efficient separation and purification method by microwave-assisted extraction coupled with counter-current Chromatography and Preparative Liquid Chromatography was developed. The extracts obtained from microwave-assisted extraction were rapid separated with counter-current Chromatography, and then the fractions were further purified with Preparative Liquid Chromatography. With this method, six furocoumarins including xanthotoxin, bergapten, columbianetin acetate, osthole, isoimperatorin and columbianadin can be obtained from original Angelica Pubescentis Radix samples within total time of 450 min. Their purities were 98%, 98%, 99%, 99%, 99% and 99% respectively, as determined by HPLC. The structures of these compounds were identified by 1H NMR and MS spectroscopy. The proposed method was economic, rapid and effective, and it can be used to prepare and purify targets from natural products.