11 Chromatographic techniques
K. WILSON
11.1 Principles of chromatography
11.2 Chromatographic performance parameters
11.3 High-performance liquid chromatography
11.4 Adsorption chromatography
11.5 Partition chromatography
11.6 Ion-exchange chromatography
11.7 Molecular (size) exclusion chromatography
11.8 Affinity chromatography
11.9 Gas chromatography
11.10 Suggestions for further reading
11.1 PRINCIPLES OF CHROMATOGRAPHY
11.1.1 Distribution coefficients
The basis of all forms of chromatography is thedistributionorpartition coefficient
(Kd), which describes the way in which a compound (theanalyte)distributes between
two immiscible phases. For two such phases A and B, the value for this coefficient is a
constant at a given temperature and is given by the expression:
concentration in phase A
concentration in phase B
¼Kd ð 11 : 1 Þ
The termeffective distribution coefficientis defined as the total amount, as distinct
from the concentration, of analyte present in one phase divided by the total amount
present in the other phase. It is in fact the distribution coefficient multiplied by
the ratio of the volumes of the two phases present. If the distribution coefficient of
an analyte between two phases A and B is 1, and if this analyte is distributed
between 10 cm^3 of A and 1 cm^3 of B, the concentration in the two phases will be the
same, but the total amount of the analyte in phase A will be 10 times the amount in
phase B.
All chromatographic systems consist of thestationary phase, which may be a solid,
gel, liquid or a solid/liquid mixture that is immobilised, and themobile phase, which
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