Column area, chromatographic scale

If you have developed a chromatographic procedure to separate 2 mg of a mixture on a column with a diameter of 1.0 cm, what size column should you use to separate 20 mg of the mixture The most straightforward way to scale up is to maintain the same column length and to increase the cross-sectional area to maintain a constant ratio of sample mass to column volume. Because cross-sectional area is nr2, where r is the column radius, the desired diameter is given by... 

In recent years h.p.l.c. has become a valuable chromatographic tool for analytical and preparative scale work. In this latter area the separation of isomers (structural, diastereoisomeric, and enantiomeric) has been possible by the selection of appropriate column packing material and solvent systems. However, the equipment, operating costs, and column packing materials are more expensive than those in t.l.c., g.l.c. and conventional liquid-solid column chromatography. 

Chromatographic resins contain a great deal of surface area, and a clear understanding of what is occurring on the surface in terms of carryover of risk factors is not always possible. Cleaning and sanitization, as well as column lifetime, are issues that must be addressed in development and validated at pilot or full scale. 

Fortunately, the effects of most mobile-phase characteristics such as the nature and concentration of organic solvent or ionic additives the temperature, the pH, or the bioactivity and the relative retentiveness of a particular polypeptide or protein can be ascertained very readily from very small-scale batch test tube pilot experiments. Similarly, the influence of some sorbent variables, such as the effect of ligand composition, particle sizes, or pore diameter distribution can be ascertained from small-scale batch experiments. However, it is clear that the isothermal binding behavior of many polypeptides or proteins in static batch systems can vary significantly from what is observed in dynamic systems as usually practiced in a packed or expanded bed in column chromatographic systems. This behavior is not only related to issues of different accessibility of the polypeptides or proteins to the stationary phase surface area and hence different loading capacities, but also involves the complex relationships between diffusion kinetics and adsorption kinetics in the overall mass transport phenomenon. Thus, the more subtle effects associated with the influence of feedstock loading concentration on the... 

In other areas of technology such as chromatographic separations, and hydrometallurgy which may often involve resin transfer (movement) operations, fluidized beds, and truly countercurrent contact of resin and liquid, the acquisition of design data is more often through a fluid dynamic and mass transfer approach to describe, and thereby scale up, column designs in order to realize commercial practices. A text of this nature is neither the vehicle for, nor can it do justice to, such an important topic and the reader is referred to the bibliography for a more detailed account of column dynamics. 

Fig. 7.4. The effect of salt concentration on capacity factor, k. Chromatographic conditions column, Partisil 1025 ODS (250 mmx4.6 mm I.D.) mobile phase, the concentration of KCl in a 0.05 M KH2PO4 solution was varied flow rate, 1 ml/min temperature, 25 °C detection, UV at 254 nm. The upper scale shows the surface tension of the eluent. The hydrocarbonaceous surface area (HSA) and the total surface area (TSA) of the solute molecules are shown. Reproduced from Horvath et al. (1976),...

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