Multicolumn countercurrent solvent gradient purification
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MCSGP is "Multicolumn Countercurrent Solvent Gradient Purification".
Biomolecules are often purified via solvent gradient batch chromatography. Here smooth linear solvent gradients are applied to carefully handle the separation between the desired component and hundreds of impurities. The desired product is usually intermediate between weakly and strongly adsorbing impurities. A center cut is required to get the desired pure product. Often the preparative resins have a low efficiency due to strong axial dispersion and slow mass transfer. Then a purification in one chromatographic step is not possible. Countercurrent movement as known from the SMB process would be required. For large scale productions and for very valuable molecules countercurrent solid movement need to be applied to increase the separation efficiency, the yield and the productivity of the purification. The MCSGP process combines both techniques in one process, the countercurrent SMB principle and the solvent gradient batch technique.
The MCSGP-process consists of several chromatographic columns, which are switched in position opposite to the flow direction. Most of the columns are equipped with a gradient pump to adjust the modifier concentration at the column inlet. Some columns are connected directly, so that non pure product streams are internally recycled. Other columns are short circuited, so that they operate in pure batch mode. The system is split into several sections, from which every section performs a tasks analog to the tasks of a batch purification. These tasks are loading the feed, running the gradient elution, recycling of weakly adsorbing site fractions, fractionation of the purified product, recycling of strongly adsorbing site fractions, cleaning the column from strongly adsorbing impurities, cleaning in place (CIP) and re-equilibration of the column to start the next purification run. All of the tasks mentioned here are carried out at the same time in one unit. Recycling of non pure site fractions is performed in countercurrent movement.
The fully continuous process consists of at least 6 columns. Semi-continuous operation with only 3 columns shows the same performance and it can even have a higher productivity.
The main advantages with respect to solvent gradient batch chromatography are high yields also for difficult separations, less solvent consumption, higher productivity, usage of countercurrent solid movement, which increases the separation efficiency. The process is continuous. Once a steady state is reached, it delivers continuously purified product in constant quality and quantity. Automatic cleaning in place is integrated. A pure empirical design of the operating conditions from a single solvent gradient batch chromatogram is possible.
Applications are all chromatographic purifications and separations, which are executed via solvent gradient batch chromatography. Typical examples are reversed phase purification of peptides, hydrophobic interaction chromatography or for example ion exchange chromatography of proteins or antibodies. The process can effectively enrich components, which have been fed in only small amounts. Continuous capturing of antibodies without affinity chromatography can be realized with the MCSGP-process.
