Continuous chromatographic

The slowly rising foam in a tall column can Be employed as the sorbent for continuous chromatographic separations [Talman and Rubin, Sep. Sci., 11, 509 (1976)]. Low gas rates are also employed in short columns to produce the scumlike froth of batch-operated ion flotation, microflotation, and precipitate flotation. 

Pais L. S., Loureiro J. M., Rodrigues A. E. (1997b) Modeling, Simulation and Operation of a Simulated Moving Bed for Continuous Chromatographic Separation of l,l -bi-2-naphthol Enantiomers, J. Chromatogr. A 769 25-35. 

Hypersorption A continuous chromatographic separation process using a moving bed. Invented in 1919 by F. D. Soddy (famed for his work on isotopes) at Oxford and developed commercially for petroleum refinery separations by the Union Oil Company of California in 1946. Six plants were built in the late 1940s, using activated carbon as the adsorbent. The process was abandoned because attrition of the bed particles proved uneconomic. 

Membrane absorbers are continuous chromatographic supports, which circumvent some of the above-mentioned problems of particulate stationary phases. They were originally derived from membrane (filtration) technology. The immobilization of interactive (ionic, hydrophobic, or biospecific) groups on the surface of microfiltration membranes was found to increase the selectivity of certain separation procedure. Ideally such activated membranes, or membrane adsorbers, allow the selective adsorption of certain substances and substance classes, which may subsequently be eluted by means of a stepwise change of the mobile phase (elution buffer). More complete information on the various types of modern membrane technology can be found in some recent reviews [e.g., 31-33]. 

The same group also performed experiments with a continuous chromatographic reactor of the SMBR type [133,174]. The system used consisted of 12 columns with inner diameters of 5.4 cm and a length of 75 cm. Approximately 12 cycles were necessary for stabilization of the system. Complete inversion of sucrose even at feed concentrations of up to 55% w/v was achieved, while the product purity was over 90%. After prolonged usage, the system efficiency decreases due to the loss of the calcium ions from the matrix and a consequent decreased selectivity of the resin. However, this problem could be overcome by regeneration of the resin with calcium nitrate. 

Figure 19.11. Diagrammatic representation of the principle of operation of a Semi-Continuous Chromatographic Refiner. Open and closed circles show schematically the concentrations of the two components being separated. The distance from feed point to product 1 offtake and from feed point to carrier fluid inlet must be sufficient to allow the required purity levels to be achieved against the usual band-spreading process...

Barker, P. E. (1971) Continuous chromatographic techniques, in A. Zlatkis and V. Pretorius (eds) Preparative Gas Chromatography, Wiley-Interscience, New York. pp. 325-394. 

VARICOL A continuous chromatographic process for separating natural products. It generally resembles the Sorbex process, which uses a simulated moving bed, but the column is divided into a larger number of independent sectors. 

The most common software tools used for chromatographic method development are optimization packages. All of these tools take advantage of the fact that the retention of a given compound will change in a predictable manner as a function of virtually any continuous chromatographic variable. 

Ludemann-Hombourger O., Nicoud R.M. and Bailly M., The Varicol process a new multicolumn continuous chromatographic process, Sep. Sci. Technol. 35 (2000) pp. 1829-1862. 

Preparative chromatography is a proven technology for the separation of specialty chemicals mainly in food and pharmaceutical industries, particularly the enantioseparation of chiral compounds on chiral stationary phases. The potential of preparative chromatographic systems were further increased by the development of continuous chromatographic processes like the simulated moving bed (SMB) process. Compared to the batch column chromatography, the SMB process offers better performance in terms of productivity and solvent consumption [2]. 

The limitations of standard reversed-phase materials have been partially overcome by introducing modem, specially deactivated hydrocarbon-silica pha.ses ]126]. the hydrocarbonaceous phases immobilized on alumina or zirconia support ]127] and the polymeric materials ]128]. Using the latter two types of stationary phase materials one can determine the HPLC capacity factors at acidic, neutral and alkaline conditions. This way a universal, continuous chromatographic hydrophobicity scale can be constructed like the standard log P scale ] 129]. 

Pedeferri, M. Petrozzi, S. Mazzotti, M. Morbidelli, M., Design and Operation of a HPLC-SMB Laboratory Unit for Continuous Chromatographic Separations. CHIMICA OGGI 1998 (March/April), 38. 

Table 8.1 overviews the different approaches that have been applied for continuous chromatographic reactors in the liquid phase. 

Table 8.1 Modeling approaches for continuous chromatographic reactors.

Barker, P.E., Ganetsos, G., Ajongwen, J., Alcin-toye, A. Bioreaction-separation on continuous chromatographic systems, Chem. Eng.J., 1992, 50, B23-B28. 

Pais, L., Loureiro, J., Rodrigues, A. Modeling, simulation and operation of a simulated moving bed for continuous chromatographic separation of l,l-bi-2-naphthol enantiomers,... 

Saska, M Clarke, S. J., Wu, M. D., Iqbal, K. Applications of continuous chromatographic separation in the sugar industry, Part I. Glu-cose/fructose equilibria on Dowex Monosphere 99 Ca resin at high sugar concentrations, Int. Sugar J., 1991, 93, 1115. 

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