Chromatography membranes scale

At present moment, no generally feasible method exists for the large-scale production of optically pure products. Although for the separation of virtually every racemic mixture an analytical method is available (gas chromatography, liquid chromatography or capillary electrophoresis), this is not the case for the separation of racemic mixtures on an industrial scale. The most widely applied method for the separation of racemic mixtures is diastereomeric salt crystallization [1]. However, this usually requires many steps, making the process complicated and inducing considerable losses of valuable product. In order to avoid the problems associated with diastereomeric salt crystallization, membrane-based processes may be considered as a viable alternative. 

The use of microporous membranes as a chromatography matrix avoids intraparticle diffusional limitations, since their pores, around two orders of magnitude larger than those of conventional resins, are accessed mainly by convection (Figure 12.10). This enables the operation at relatively high flow rates, with relatively low pressure drops. Additionally, membrane adsorbers present better mechanical resistance than gels, with no deformation and bed compaction problems. Also, the systems are usually modular and easy to scale up (Klein, 2000 Bueno and Miranda, 2005). 

Fig. 7 Membranes can be formed by components of carbonaceous meteorites [69,70]. a The Murchison meteorite contains approximately 2% organic carbon by weight, b Organic compounds can be extracted from the meteorite by a lipid solvent system (chloroform-methanol), then separated by two-dimensional chromatography. Polycyclic compounds in the mixture produce fluorescent spots, c The organic acid fraction from the TLC plate readily assembles into membranous vesicles when exposed to dilute aqueous solutions buffered at pH 8-9. The vesicles were photographed by their autofluorescence. Scale bar shows 20 im...

However, it can be assumed for most electrochemical applications of ionic liquids, especially for electroplating, that suitable regeneration procedures can be found. This is first, because transfer of several regeneration options that have been established for aqueous solutions should be possible, allowing regeneration and reuse of ionic liquid based electrolytes. Secondly, for purification of fiesh ionic liquids on the laboratory scale a number of methods, such as distillation, recrystallization, extraction, membrane filtration, batch adsorption and semi-continuous adsorption in a chromatography column, have already been tested. The recovery of ionic liquids from rinse or washing water, e.g. by nanofiltration, can also be an important issue. 

This study focuses firstly on the transfer of regeneration principles as they have been developed in the field of water-based electroplating and of purification options for ionic liquids as they are experienced in other fields of ionic liquid application. A number of purification procedures for fresh ionic liquids have already been tested on the laboratory scale with respect to their finishing in downstream processing. These include distillation, recrystallization, extraction, membrane filtration, batch adsorption and semi-continuous chromatography. But little is known yet about efficiency on the technical scale. Another important aspect discussed is the recovery of ionic liquids from rinse or washing water. 

The use of partition coefficients between water and lipophilic media is of wide use in pharmaceutical research. As discussed in the last chapters, different lipophilicity scales are used to describe the lipophilicity of a compound and relate it to its absorption behaviour in vivo. Differences between the logPow and partitioning between phospholipids and water (mainly determined using liposomes) for diverse compounds have been described leading to the development of the immobilized artificial membrane chromatography system. However, also the predictivity of the IAM system is limited and only a small number of membrane systems are available. 

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