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

e disrupted, however, if the capillary internal diameter is
too wide (³200 to 300 µm). In this case, surface tension
becomes insufficient to uniformly drag the center portion
of the liquid at the velocity generated at the walls. Details of
the effect of the flow profile on peak shape are given in
sections 2.3.4 Dispersion and 2.3.4.1 Factors Affecting
Efficiency.
Another benefit of the EOF is that it causes movement of
nearly all species, regardless of charge, in the same direction.
Under normal conditions (that is, negatively charged
capillary surface), the flow is from the anode to the cathode.
Anions will be flushed towards the cathode since the
magnitude of the flow can be more than an order of magnitude
greater than their electrophoretic mobilities. Thus
cations, neutrals, and anions can be electrophoresed in a
single run since they all “migrate” in the same direction.
This process is depicted in figure 8. Here, cations migrate
fastest since the electrophoretic attraction towards the
cathode and the EOF are in the same direction, neutrals are
all carried at the velocity of the EOF but are not separated
Principles
Figure 8
Differential solute migration superimposed
on electro-osmotic flow in
capillary zone electrophoresis
from each other, and anions migrate slowest since they are
attracted to the anode but are still carried by the EOF
toward the cathode.
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