Chromatographic band profiles and band separation of enantiomers at high concentration

Jacobson, Stephen C.; Golshan-Shirazi, Sadroddin; Guiochon, Georges

doi:10.1021/ja00174a007

Cited by 136 publications

(82 citation statements)

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“…In some reports, it is suggested that the saturation capacity of type-II sites is the same for the two enantiomers. 7 This result is not general, however. There are obvious reasons for which the saturation capacity of the type-II sites could be different for the two enantiomers.…”

Section: Adsorption Isotherms On Chiral Stationary Phasesmentioning

confidence: 88%

“…This explains why some workers have been able to derive wrong conclusions. 29 Using this procedure, we studied the separation of several pairs of enantiomers: N-benzoyl derivatives of several amino acids and methyl mandelate on immobilized BSA, 6,30,31 ketoprofen and methyl mandelate on an immobilized cellulose derivative; 7,32 Tröger's base on microcrystalline cellulose triacetate; [33][34][35][36] and propranolol on cellobiohydrolase I (CBH I), a protein bonded to silica. 9,24 Only in the case of Tröger's base was it not possible to resolve the two contributions, because the more retained S-isomer has an S-shaped isotherm while the R-isomer follows Langmuir adsorption behavior.…”

Section: Adsorption Isotherms On Chiral Stationary Phasesmentioning

confidence: 99%

“…Note that the reliability of the isotherm is verified by the excellent agreement between measured and calculated band profiles. [7][8][9]24,26,[30][31][32][33][34][35][36] The two Langmuir contributions correspond, respectively, to the enantioselective and the nonselective interactions. If the data are fitted to the set of Eqs.…”

Section: Adsorption Isotherms On Chiral Stationary Phasesmentioning

confidence: 99%

“…The few attempts made, although still limited in scope, have illustrated the potential interest of a systematic approach. [7][8][9] We can distinguish two types of chiral stationary phases (CSP), those that are obtained by chemically bonding ligands with localized chiral center and those that are derived from natural products (e.g., cellulose) and in which a high proportion of the carbon atoms have a well-defined chirality. In the latter type, the whole solution is a chiral environment, most molecular interactions are chiral and do not need to be strong.…”

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A closer study of chiral retention mechanisms

1998

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Section: Adsorption Isotherms On Chiral Stationary Phasesmentioning

confidence: 88%

Section: Adsorption Isotherms On Chiral Stationary Phasesmentioning

confidence: 99%

Section: Adsorption Isotherms On Chiral Stationary Phasesmentioning

confidence: 99%

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A closer study of chiral retention mechanisms

1998

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“…The bi-Langmuir isotherm model [17] is important in chiral separations since the first of the two Langmuir components can be identified as accounting for the nonselective interactions, the second for the selective interactions between the enantiomers and the enantioselective adsorbent. It is written as …”

Section: The Competitive Bi-langmuir Adsorption Isothermmentioning

confidence: 99%

A modified coupled complex boundary method for an inverse chromatography problem

Cheng

Lin

Zhang

et al. 2017

Journal of Inverse and Ill-Posed Problems

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Adsorption isotherms are the most important parameters in rigorous models of chromatographic processes. In this paper, in order to recover adsorption isotherms, we consider a coupled complex boundary method (CCBM), which was previously proposed for solving an inverse source problem [2]. With CCBM, the original boundary fitting problem is transferred to a domain fitting problem. Thus, this method has advantages regarding robustness and computation in reconstruction. In contrast to the traditional CCBM, for the sake of the reduction of computational complexity and computational cost, the recovered adsorption isotherm only corresponds to the real part of the solution of a forward complex initial boundary value problem. Furthermore, we take into account the position of the profiles and apply the momentum criterion to improve the optimization progress. Using Tikhonov regularization, the well-posedness, convergence properties and regularization parameter selection methods are studied. Based on an adjoint technique, we derive the exact Jacobian of the objective function and give an algorithm to reconstruct the adsorption isotherm. Finally, numerical simulations are given to show the feasibility and efficiency of the proposed regularization method.

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Apparent and true enantioselectivity in enantioseparations

2000

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The separation factor of two compounds in chromatography is the ratio of their equilibrium constants or retention factors. This parameter is universally employed to investigate their resolution and to optimize the experimental conditions of their analysis. In enantioseparations, the situation is more complex because there is a mixed retention mechanism. The retention factor is the sum of two contributions, one enantioselective, the other nonselective. Although both contribute to retention, the latter being identical for the two enantiomers and does not contribute to their separation. We show how these two contributions can be measured and how it becomes necessary to distinguish between the apparent, alpha(app), and the true, alpha(true), separation factors. The existence of nonselective sites is responsible for alpha(app) being less than alpha(true). Depending on the difference between these two factors, the more effective approach to improve a separation is either to increase the enantioselectivity or to reduce the nonselective interactions. Practical applications to separations of different beta-blockers on cellobiohydrolase are discussed. The apparent enantioselectivity of alprenolol is larger and increases faster with increasing pH than that of the more hydrophobic propranolol, in spite of the importance of hydrophobic interactions in the enantioselective mechanism. These two unexpected properties are discussed and explained.

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Chromatographic band profiles and band separation of enantiomers at high concentration

Cited by 136 publications

References 0 publications

A closer study of chiral retention mechanisms

A closer study of chiral retention mechanisms

A modified coupled complex boundary method for an inverse chromatography problem

Apparent and true enantioselectivity in enantioseparations

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