Page 324 - Biosystems Engineering

Bioseparation Pr ocesses 301

can be solid or liquid, whereas the mobile phase can be liquid or gas.
Various types of chromatographic methods are used to separate bio-
logical compounds:

1. Column chromatography
2. Paper chromatography
3. Ion-exchange chromatography
4. Gel filtration chromatography
5. Affinity chromatography

Column Chromatography
Column chromatography is an adsorption chromatography where
compounds are adsorbed onto silica or alumina in a column. An equi-
librium is set up between molecules bound to the column and those
free in solution (Fig. 9.6). The charge, van der Waals forces, dipole
interactions, hydrogen bonding stearic factors, and structure of the
compounds govern the extent of binding. Thus, the choice of correct
adsorbent and solvent is, to a large extent, dependent on the polarity
of the compounds. It is also essential that the mixture be soluble in
the solvent; otherwise, it will remain permanently adsorbed in the
adsorbent.

Slurry 1 wet settled volume + 0.5
volume of solvent

Glass rod to avoid trapping air bubble

Adsorbent

Glass wool

FIGURE 9.6 Chromatographic column.