Preparative gradient chromatography

During a chromatographic separation, it is convenient to keep the essential operating parameters like temperature, pressure, mobile phase flow-rate, and mobile phase composition constant. Though, it is well known that in contrast to this isocratic operation the intelligent modulation of certain operating parameters can improve the separation performance significantly. Such gradient approaches are widely applied in analytical (linear) chromatography to reduce the time of analysis and to enhance the selectivity. In contrast, the extent of application of these gradients is still rather limited in the field of preparative (nonlinear) chromatography. The first part of this paper is devoted to the discussion of the principal differences between linear and nonlinear and isocratic and gradient chromatography. The second part focuses on introducing a countercurrent process that allows separation in a continuous manner, efficiently exploiting a two-step solvent composition gradient. Copyright © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim [accessed February 8th 2013

Purification of Curcumin from Ternary Extract-Similar Mixtures of Curcuminoids in a Single Crystallization Step

Crystallization-based separation of curcumin from ternary mixtures of curcuminoids having compositions comparable to commercial extracts was studied experimentally. Based on solubility and supersolubility data of both, pure curcumin and curcumin in presence of the two major impurities demethoxycurcumin (DMC) and bis(demethoxy)curcumin (BDMC), seeded cooling crystallization procedures were derived using acetone, acetonitrile and 50/50 (wt/wt) mixtures of acetone/2-propanol and acetone/acetonitrile as solvents. Starting from initial curcumin contents of 67–75% in the curcuminoid mixtures single step crystallization processes provided crystalline curcumin free of BDMC at residual DMC contents of 0.6–9.9%. Curcumin at highest purity of 99.4% was obtained from a 50/50 (wt/wt) acetone/2-propanol solution in a single crystallization step. It is demonstrated that the total product yield can be significantly enhanced via addition of water, 2-propanol and acetonitrile as anti-solvents at the end of a cooling crystallization process

Analysis of Reacting Mixtures in a Heat Integrated Simulated Moving Bed Reactor

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