High performance capillary electrophoresis - T.E.A.M.

Principles
Figure 19
Electrodispersion due to mismatched
sample and buffer conductivities
2.3.4.5 Electrodispersion
Differences in sample zone and running buffer conductivities
can have three major effects: 1) skewed peak shapes;
2) solute concentration or focusing (low conductivity
sample), or solute defocusing (high conductivity sample);
3) temporary isotachophoretic states due to excess of a
certain ion (for example, Cl - ).
As described by the Kohlrausch regulating function, when
the solute zone has a higher mobility than the running
buffer, the leading edge of the solute zone will be diffuse
and the trailing edge sharp. Conversely, when the solute
zone has a lower mobility than the running buffer, the leading
edge will be sharp and the trailing edge diffuse. When
the conductivities are equivalent, no such peak distortions
will occur. Schematics of each case are shown in figure 19.
a) b) c)
Low
conductivity
High
conductivity
Low
conductivity
Equivalent
High
conductivity
Low
conductivity
High
conductivity
Sample zone Sample zone Sample zone
E
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