The Economics of Chromatographic Separations

The purity of a component, i, is the concentration of this component in the collected fraction (solvent excluded). It is given by 

As we discuss in the next section, the amount of solvent consumed per unit amount of purified product prepared is an important contribution to the total cost of production in many cases. The amount of solvent used during a cycle is the product of the cycle time and the flow rate. The amoimt produced per cycle is the product of the amount injected and the recovery yield. Thus the solvent consumption is given by 

Alternatively, we can consider the amoimt of purified component produced per unit volume of solvent used. This amount is the specific production and it is equal to 

The specific production, the production rate, and the recovery yield are used for the definition of objective functions. 

Different authors have previously discussed the economics of preparative chromatographic separations [12-14], The main difficulty of the exercise is in the separation of the technical and the economic parameters. The influences of the various technical parameters of the process on the characteristics of the production performance are easy to figme out. They can be discussed in detail relatively independently of the specific details of a given separation problem. By contrast, the economic parameters are usually very specific to a product and even to the company that runs the separation and they are never constant over the long term. 

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In the chemical industry, chromatographic separation process is an emerging technology for the separation of pharmaceutical products, food and fine chemicals. To improve the economic viability, a continuous countercurrent operation is often desirable but the actual movement of the solid leads to a serious operating problem. Therefore, the simulated moving bed (SMB) process is an interesting alternative option. 

In practical terms, the purification of aqueous solutions of XX on Rohm and Haas macroreticular resin XAD-16 proved to be very efficient (95-98% recovery of material with a purity of approximately 95%) and economical to carry out. This chromatographic purification step removes salts (especially phosphates) introduced at earlier processing steps in Antibioticos plant (Schemes 1 and 2), thereby enabling us to minimize the amount of DDM needed to fully esterify both carboxyl groups of XX 2.3 to 2.5 moles DDM per mole of XX generally proved sufficient.31 Although DDM is a relatively stable molecule (see footnote 20), its separate preparation does introduce some safety concerns. In practical terms, it should be possible to prepare... 

The advantages of egg yolk antibodies with respect to the welfare of animals and to scientific and economic considerations are described in a recent review.50 Although antibodies issued from this source are mostly used in laboratories and for diagnostics, they must be extracted and purified from very complex mixtures. The presence of massive amount of insoluble material and lipids is the most important problem. The collected egg yolk must first be clarified and the lipid removed for a consistent chromatographic separation. Table 3 summarizes the most important characteristics of expression systems for antibody preparation with regards to the chromatographic separation. 

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