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

Modes
The separation mechanism of neutral solutes in MEKC is
essentially chromatographic and can be described using
modified chromatographic relationships. The ratio of the
total moles of solute in the micelle (that is, the pseudostationary
phase) to those in the mobile phase, the capacity
factor, k', is given by:
(t r
– t 0
) V
k' = S
t 0
1 – t = K (24)
r
V M
( t m
)
( )
where t r
= retention time of the solute,
t 0
= retention time of unretained solute
moving at the EOF rate (or “dead time”)
t m
= micelle retention time
K = partition coefficient
V S
= volume of the micellar phase
V M
= volume of the mobile phase.
This equation is modified from the normal chromatographic
description of k' to account for movement of the pseudostationary
phase. Note that as t m
becomes infinite (that is,
the micelle becomes truly stationary) the equation reduces
to its conventional form.
Resolution of two species in MEKC can be described by
R =
(
1 –
t m
)
4 a k' 2
+ 1 1 – t 0 k 1
N
( 1/2 a – 1 k'
)( )( 2
)
Efficiency Selectivity
where a = k 2
' / k 1
'
Retention
t 0
( )
( )
t m
(25)
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