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Andreas Seidel-morgenstern - One of the best experts on this subject based on the ideXlab platform.

  • Chapter 25 – Process concepts in Preparative Chromatography
    Liquid Chromatography, 2017
    Co-Authors: Malte Kaspereit, Andreas Seidel-morgenstern
    Abstract:

    This chapter describes different rivaling operating modes applied industrially in Preparative Chromatography. After recapitulating the basic features of the “workhorse” and reference in the field, namely isocratic batch elution, at first more sophisticated concepts are presented that offer additional degrees of freedom but maintain the discontinuous character of the separation process. Subsequently process options are described that possess the potential to perform the separations continuously. Hereby mainly the most successful multicolumn concepts are explained, which are based on realizing highly efficient countercurrent transport processes. Finally the important aspect will be addressed, how different process alternatives can be evaluated and compared quantitatively.

  • Processes to Separate Enantiomers
    ChemInform, 2014
    Co-Authors: Heike Lorenz, Andreas Seidel-morgenstern
    Abstract:

    Review: [enantioselective crystallization, Preparative Chromatography or a combination of both processes; 315 refs.

  • Process concepts in Preparative Chromatography
    Liquid Chromatography, 2013
    Co-Authors: Malte Kaspereit, Andreas Seidel-morgenstern
    Abstract:

    Abstract This chapter describes different rivaling operating modes applied industrially in Preparative Chromatography. After recapitulating the basic features of the “workhorse” and reference in the field, namely isocratic batch elution, at first more sophisticated concepts are presented that offer additional degrees of freedom but maintain the discontinuous character of the separation process. Subsequently process options are described that possess the potential to perform the separations continuously. Hereby mainly the most successful multicolumn concepts are explained, which are based on realizing highly efficient countercurrent transport processes. Finally the important aspect will be addressed, how different process alternatives can be evaluated and compared quantitatively.

  • Theoretical study of Preparative Chromatography using closed-loop recycling with an initial gradient
    Journal of chromatography. A, 2009
    Co-Authors: Balamurali Sreedhar, Andualem Damtew, Andreas Seidel-morgenstern
    Abstract:

    Complementing classical isocratic elution, several more sophisticated operating modes have been proposed and are applied in Preparative Chromatography in order to improve performance. One such approach is gradient elution, where the solvent strength is altered by varying the fraction of a modifier added to the mobile phase to enhance selectivity and to achieve faster elution. Another useful technique is closed-loop recycling, allowing better peak resolution and increased yields. This study focuses on a modified new scheme which incorporates the advantages of both gradient elution and closed-loop recycling for the separation of a ternary mixture where the intermediately eluting component is the target. A parametric study was carried out using typical adsorption isotherm parameters to elucidate the effects of varying loading factors and parameters specific to the two basic operational modes on production rates and yields. A comparison was also made between the proposed scheme and conventional techniques. It was found that the studied scheme could exploit increased column loadings and offers significantly higher production rates.

  • Effects of a Strongly Adsorbed Additive on Process Performance in Chiral Preparative Chromatography
    Journal of Chromatography A, 2008
    Co-Authors: Patrik Forssén, Andreas Seidel-morgenstern, Malte Kaspereit, Robert Arnell, Torgny Fornstedt
    Abstract:

    The shapes of elution profiles are often significantly influenced by the presence of strongly adsorbed additives in the mobile phase. This aspect needs to be considered in quantitative optimization of Preparative Chromatography. The theoretical study carried out here is based on available thermodynamic information for the enantiomers of three β-blockers, alprenolol, propranolol, and atenolol, on a teicoplanin chiral stationary phase (Chirobiotic T) using methanol/acetonitrile as the mobile phase and acetic acid/triethylamine as the additive. The properties of this strong additive made it possible to tune the binary elution profiles in any combination of the following apparent band shapes: anti-Langmuir/anti-Langmuir, anti-Langmuir/Langmuir and Langmuir/Langmuir. Optimization of the productivity and yield, when performing repetitive batch injections, was investigated using the equilibrium dispersive model. We show that it is important to consider the invisible additive perturbation peak when defining the cycle time and therefore a model-based optimization needs to take this into account. Furthermore, both productivity and yield could be improved for the two unusual shape combinations in comparison to the traditional Langmuir/Langmuir case.

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

  • Effects of the surface concentration of fixed charges in C18-bonded stationary phases on the adsorption process and on the Preparative Chromatography of small ionizable compounds.
    Journal of chromatography. A, 2014
    Co-Authors: Fabrice Gritti, Georges Guiochon
    Abstract:

    The effects of the surface concentration of positive charges attached to the surface of research BEH-C18 hybrid particles on the overloaded band profiles and the adsorption isotherms of a neutral (caffeine) and a positively charged (nortryptilinium hydrochloride) compounds were measured and investigated. The inverse method (IM) of Chromatography was used to determine the isotherm parameters. Three columns were packed with endcapped BEH-C18 particles doped with three different charge densities on their surfaces (LOW, MEDIUM and HIGH). Two other columns packed with unbonded, non-endcapped, and endcapped BEH-C18 particles served as standard reference materials. Minor disturbance method (MDM) experiments were conducted with acetonitrile/water mixtures in order to assess qualitatively the surface densities of the fixed positive charges. A more quantitative approach based on the solution of the linearized Poisson-Boltzmann equation and the decrease of the experimental Henry constant was also applied. The results show that the surface concentrations of the fixed charges in the LOW, MEDIUM and HIGH columns were 0.029, 0.050, and 0.064μmol/m2, e.g., close to two orders of magnitude smaller than the surface density of bonded C18 chains (2.1μmol/m2). The adsorption isotherm of the ionizable compound nortryptilinium onto the BEH-C18 columns is consistent with a two-sites adsorption model. The density of the high energy sites correlates directly to the total amount of the fixed charges and isolated silanols amidst the C18-bonded chains. The amount of low energy sites reflects the specific surface area of the adsorbent. The binding constants on the high- and low-energy adsorption sites are respectively ten and two times lower on the HIGH column than on the reference endcapped column. The active sites are closer to the adsorbent surface than the weak adsorption sites. Finally, a higher production rate of ionizable compounds can be achieved in Preparative Chromatography with the charge doped than with the reference RPLC-C18 columns. For the same analysis time, larger recovery yields are observed despite a slight loss in selectivity due to non-selective repulsive electrostatic interactions.

  • Theoretical study of recycling in Preparative Chromatography
    AIChE Journal, 1993
    Co-Authors: Andreas Seidel-morgenstern, Georges Guiochon
    Abstract:

    Using the equilibrium-dispersive model of Chromatography, we have investigated recycling as a means to improve the recovery yields and possibly the production rates of chromatographic separations. When compared with the optimal values obtained for the conventional single-cycle regime, our results prove the potential for recycling in Preparative Chromatography. The analysis performed for the separation of two binary mixtures demonstrates that recycling not only improves the recovery yield but can increase the production rate under certain conditions. Different possibilities of collecting sufficiently separated fractions during recycling are compared. The mathematical model developed can be used effectively for designing optimal recycling strategies in Preparative liquid Chromatography.

  • Isotherm selection for band profile simulations in Preparative Chromatography
    AIChE Journal, 1991
    Co-Authors: Stephen C. Jacobson, Sadroddin Golshan-shirazi, Georges Guiochon
    Abstract:

    Equilibrium adsorption data for the N-benzoyl derivatives of D- and L-phenyl alanine in water/propanol solutions have been determined on a chiral-selective stationary phase, bovine serum albumin immobilized on silica. These data are well accounted for by an isotherm equation resulting from the sum of two Langmuir terms. The first term corresponds to the chiral-selective interactions, and the second to the nonselective molecular interactions between the enantiomers and the stationary phase. The individual band profiles of the two enantiomeric amino acids, either pure or in binary mixtures of various compositions, are predicted exactly by an equilibrium dispersive model using this bi-Langmuir isotherm. A classical Langmuir isotherm fails to predict these band profiles, illustrating the importance to collect accurate adsorption data and to use a correct isotherm model when calculating chromatographic band profiles.

Torgny Fornstedt - One of the best experts on this subject based on the ideXlab platform.

  • Chapter 24 - Modeling of Preparative liquid Chromatography
    Liquid Chromatography, 2017
    Co-Authors: Torgny Fornstedt, Patrik Forssén, Jörgen Samuelsson
    Abstract:

    Preparative Chromatography is the best generic method today for the purification of small drugs and valuable chemical components at

  • Modeling of Preparative Liquid Chromatography
    Liquid Chromatography, 2013
    Co-Authors: Torgny Fornstedt, Patrik Forssén, Jörgen Samuelsson
    Abstract:

    Preparative Chromatography is today the best generic method for the purification of small drugs and valuable chemical components at the

  • A quest for the optimal additive in chiral Preparative Chromatography.
    Journal of chromatography. A, 2009
    Co-Authors: Patrik Forssén, Robert Arnell, Torgny Fornstedt
    Abstract:

    Traditionally, the choice of acid/base additives used in chiral Preparative Chromatography has not been considered very important. However, it was recently demonstrated that strongly adsorbing additives can result in the most unexpected enantiomer band shapes in modern chiral Preparative chromatographic systems. In the present study we demonstrate that, depending on the choice of additive, it is actually possible to obtain the following four binary band-shape compositions when a racemic mixture is injected: (i) anti-Langmuir/anti-Langmuir, (ii) anti-Langmuir/Langmuir, (iii) Langmuir/Langmuir and (iv) Langmuir/anti-Langmuir. Further, we made an advanced numerical investigation, in order to ascertain which one of the four band-shape compositions, is the most favourable one in Preparative batch Chromatography of a racemic mixture. We found that if the target for purification is either the first eluting enantiomer or both ones, the traditional Langmuir/Langmuir band-shape composition should be chosen. But, if only the second eluting enantiomer is to be purified the optimal situation is the anti-Langmuir/Langmuir band-shape composition. Thus, it was concluded that the best choice of additive depends on which enantiomer is of interest and it is useful to perform a thorough additive screening to find the optimal additive, giving the most advantageous peak shape composition and accordingly the best process performance for a particular separation problem.

  • Effects of a Strongly Adsorbed Additive on Process Performance in Chiral Preparative Chromatography
    Journal of Chromatography A, 2008
    Co-Authors: Patrik Forssén, Andreas Seidel-morgenstern, Malte Kaspereit, Robert Arnell, Torgny Fornstedt
    Abstract:

    The shapes of elution profiles are often significantly influenced by the presence of strongly adsorbed additives in the mobile phase. This aspect needs to be considered in quantitative optimization of Preparative Chromatography. The theoretical study carried out here is based on available thermodynamic information for the enantiomers of three β-blockers, alprenolol, propranolol, and atenolol, on a teicoplanin chiral stationary phase (Chirobiotic T) using methanol/acetonitrile as the mobile phase and acetic acid/triethylamine as the additive. The properties of this strong additive made it possible to tune the binary elution profiles in any combination of the following apparent band shapes: anti-Langmuir/anti-Langmuir, anti-Langmuir/Langmuir and Langmuir/Langmuir. Optimization of the productivity and yield, when performing repetitive batch injections, was investigated using the equilibrium dispersive model. We show that it is important to consider the invisible additive perturbation peak when defining the cycle time and therefore a model-based optimization needs to take this into account. Furthermore, both productivity and yield could be improved for the two unusual shape combinations in comparison to the traditional Langmuir/Langmuir case.

  • Effects of a strongly adsorbed additive on process performance in chiral Preparative Chromatography.
    Journal of chromatography. A, 2008
    Co-Authors: Patrik Forssén, A. Seidel-morgenstern, Robert Arnell, M Kaspereit, Torgny Fornstedt
    Abstract:

    The shapes of elution profiles are often significantly influenced by the presence of strongly adsorbed additives in the mobile phase. This aspect needs to be considered in quantitative optimization of Preparative Chromatography. The theoretical study carried out here is based on available thermodynamic information for the enantiomers of three beta-blockers, alprenolol, propranolol, and atenolol, on a teicoplanin chiral stationary phase (Chirobiotic T) using methanol/acetonitrile as the mobile phase and acetic acid/triethylamine as the additive. The properties of this strong additive made it possible to tune the binary elution profiles in any combination of the following apparent band shapes: anti-Langmuir/anti-Langmuir, anti-Langmuir/Langmuir and Langmuir/Langmuir. Optimization of the productivity and yield, when performing repetitive batch injections, was investigated using the equilibrium dispersive model. We show that it is important to consider the invisible additive perturbation peak when defining the cycle time and therefore a model-based optimization needs to take this into account. Furthermore, both productivity and yield could be improved for the two unusual shape combinations in comparison to the traditional Langmuir/Langmuir case.

Luís S. Pais - One of the best experts on this subject based on the ideXlab platform.

  • Separation of Nadolol Racemates by High pH Reversed-Phase Preparative Chromatography
    Separation and Purification Technology, 2020
    Co-Authors: Rami S. Arafah, António E. Ribeiro, Alírio E. Rodrigues, Luís S. Pais
    Abstract:

    Abstract The separation of nadolol racemates under high pH reversed-phase Preparative Chromatography is presented for the first time. Three Waters C18 adsorbents (XBridge, Shield and XSelect) are compared for the separation of nadolol racemates using ethanol:water:diethylamine solvent mixtures. Experimental and simulation results are presented to compare the separation performances at Preparative scale using both the fixed-bed and the simulated moving bed operations. The Waters XBridge C18 adsorbent and an ethanol:water:diethylamine solvent mixture are selected as a good option for the separation of nadolol racemates. The validated methodology allows the separation of a multicomponent nadolol feed mixture composed by four stereoisomers into two pure racemates (two pairs of enantiomers). This work introduces the potential of using an initial achiral separation step in the global strategy for the complete multicomponent separation of the four nadolol stereoisomers.

Christian Heuer - One of the best experts on this subject based on the ideXlab platform.

  • Experimental and theoretical study of recycling in Preparative Chromatography
    Separation Science and Technology, 1999
    Co-Authors: Christian Heuer, Peter Hugo, Andreas Seidel-morgenstern
    Abstract:

    To recycle a sample to be separated several times over the column is an efficient tool to improve process performance in Preparative liquid Chromatography. This technique mimics the application of a longer column. It is possible to recycle the whole sample in a closed loop or to recycle only mixed fractions. The technique is simple to implement and offers a good solvent economy. Several successful applications have been reported mainly from the pharmaceutical industry. In these cases the process design was performed more or less empirically and solely based on standard parameters used in analytical Chromatography. Recently some efforts have been undertaken to develop mathematical models taking into account the features of nonlinear Chromatography and to evaluate recycling Chromatography in comparison to other rivaling techniques. In this paper experimental data will be compared with predictions of the equilibrium dispersion model. It will be shown that this model can be considered as a reliable tool for designing and optimizing recycling Chromatography. Finally, recycling is compared to standard batch elution Chromatography in terms of recovery, productivity and eluant consumption. © Informa UK Limited, an Informa Group Company [accessed 2014 October 16

  • Comparison of various process engineering concepts of Preparative Chromatography
    Chemical Engineering & Technology, 1998
    Co-Authors: Christian Heuer, Hagen Kniep, T. Falk, Andreas Seidel-morgenstern
    Abstract:

    Liquid Chromatography utilizing porous solid phases (adsorption Chromatography) is one of the most powerful and versatile methods of modern analytical chemistry. Its widespread application is due in part to the development of a broad range of combinations of solid stationary and liquid mobile phases. Normal phase and reverse phase Chromatography with pure and chemically modified silica, respectively, affinity Chromatography, can be cited as examples. In addition to its use as an analytical method, Chromatography is becoming increasingly important in the Preparative scale for the isolation of pure substances in the pharmaceutical industry, in biotechnology, and in the production of fine chemicals. In many cases, the required purity criteria can only be met with chromatographic techniques, as in the resolution of racemates. From a process engineering viewpoint, a better understanding of concentration profile deformations caused by intended overloading of separation columns has recently been acquired. In particular, this concerns the description of displacement and entrainment effects associated with the competitive adsorption. A series of alternative operating modes has been developed and used to enhance yields and productivities. In spite of a number of attempted comparative studies, quantitative information about optimizing these processes is lacking. This article will compare four different process engineering concepts of Preparative Chromatography on the basis of a uniform theoretical model.

  • Scale up in Preparative Chromatography
    Journal of Chromatography A, 1996
    Co-Authors: Christian Heuer, Peter Hugo, Gregor Mann, Andreas Seidel-morgenstern
    Abstract:

    The subject of the paper is the application of a theoretical concept to scale up Preparative Chromatography. As an experimental example, the separation of the α- and β-isomers of a steroid compound using silica as the stationary phase is discussed. The applied concept is mainly based on measuring the adsorption isotherms in preliminary investigations using an analytical column. With these thermodynamic parameters it is attempted to simulate the separation behaviour in larger columns using the equilibrium dispersive model. To check the accuracy of the approach, experimental studies have been carried out using three other columns with increasing diameters (0.8, 5 and 30 cm). On the basis of the determined adsorption isotherms and a phase ratio adjustment, the main features of the separation process can be predicted for the larger columns. Thus, the presented concept can be effectively used in the process of optimizing Preparative Chromatography.