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

The resolution of two components can also be expressed
with respect to efficiency
Principles
( )
1 Dm
R = N 1/2 (22)
4 m
where Dm= m 2
- m 1
m =
m 2
+ m 1
2
(note: time -1 or velocity can be substituted for mobility).
Substituting equation (14) into equation (22) yields a
commonly cited theoretical equation for resolution that
does not require explicit calculation of efficiency. It also
describes the effect of EOF on resolution.
( )
( ) 1/2
1 V
R = (Dm) (23)
4 Ö2 D(m + m EOF
)
In contrast to efficiency, which increases linearly with
applied voltage, a similar gain in resolution is not found, due
to the square root relationship. The voltage must be quadrupled
to double the resolution. The generation of Joule
heat often limits the benefits gained from this action.
It is evident from equation (23) that infinite resolution will
be obtained when m and m EOF
are equal but opposite. That is,
when the ion migrates in the opposite direction and at the
same rate as the EOF. In this case, however, the analysis
time approaches infinity. Clearly, the operational parameters
should be controlled so as to balance resolution and
analysis time.
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