Preparative-scale batch chromatographs

For increasing the capacity of preparative work, two methods have proved to be popular, viz., cyclic automatic operation and increasing the column diameter. These two principles, alone or in combination, should permit the scaling up of production-scale throughputs, but this aim has not yet been realized. 

Repetitive cycle operation. If the operator is required to inject each sample and to wait for the chromatograms to be produced, the task of operating in a repetitive cyclic manner becomes burdensome and the need for an automatic device rapidly becomes apparent. 

Such instruments operate unattended, and can be stopped after sufficient material has been collected. This technique can increase the economy of preparative liquid chromatography, insofar as it requires a minimum of human effort and interaction in order to separate adequate amounts of material in runs that may take several days or even v eeks. 

As a fault in a run usually leads to contamination of the material that has already been separated and collected, all results obtained prior to such a fault will be lost. Therefore, the advantages of automatic over manual operation can 

The control systems for performing such progranined separations can be arranged into three groups  

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Analytical preparative-scale batch chromatographs will satisfactorily separate and isolate individual components from mixtures in amounts sufficient for tentative identification or structural elucidation (spectroscopic and C, H, N analysis ... 

Analytical preparative-scale batch chromatographs are widely used. For analytical preparative operation on columns up to about 10 mm or more in diameter, one can use analytical instruments designed specifically for this purpose. The following components should be adapted to the preparative specifications of large analytical columns reservoir, pump, sample introduction device, detector and outlet. 

Chromatographic batch reactors are employed to prepare instable reagents on the laboratory scale (Coca et al., 1993) and for the production of fine chemicals. These applications include the racemic resolution of amino acid esters (Kalbe et al., 1989), acid-catalyzed sucrose inversion (Lauer, 1980), production of dextran (Zafar and Barker, 1988) and saccharification of starch to maltose (Sarmidi and Barker, 1993a). Sardin et al. (1993) employed batch chromatographic reactors for different esterification reactions such as the esterification of acetic acid with ethanol and the transesterification of methylacetate. Falk and Seidel-Morgenstern (2002) have investigated the hydrolysis of methyl formate. 

A simplified flow sheet for a preparative scale chromatograph is shown in Figure 10.1. Since the system is, in essence, a batch process, it is common... 

HPLC separations are one of the most important fields in the preparative resolution of enantiomers. The instrumentation improvements and the increasing choice of commercially available chiral stationary phases (CSPs) are some of the main reasons for the present significance of chromatographic resolutions at large-scale by HPLC. Proof of this interest can be seen in several reviews, and many chapters have in the past few years dealt with preparative applications of HPLC in the resolution of chiral compounds [19-23]. However, liquid chromatography has the attribute of being a batch technique and therefore is not totally convenient for production-scale, where continuous techniques are preferred by far. 

The problem here was that the target molecule is very complex and unstable. The results of the rebinding test are shown after 1 and 26 h of equilibration (expressed as peak area values). The absolute absorbance decreased during this time due to template decomposition. 2-Vinyl pyridine appeared to be the most successful monomer based on the equilibrium batch rebinding tests (Fig. 15). The 2-VPY materials prepared on a larger scale and tested as chromatographic stationary phases also exhibited a certain selectivity towards the template (methotrexate, MTX) and its closely related analogues (leucovorin and folic acid) (Fig. 16). 

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