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

Modes
UV 254 nm
0.001 AU
1
2
3
ITP has been used as a preconcentration step prior to CZE,
MEKC, or CGE. In most cases, a true ITP steady-state is not
obtained since the modes are mixed. Nonetheless, up to
30 to 50 % of the capillary can be filled with sample while
maintaining good separation quality. A difficulty often arises
with finding buffer systems that contain both leading and
trailing ions and also form the desired pH. An additional
limitation is that only cations or anions can be sharpened,
not both simultaneously.
Cl-
0 5
Time [min]
Figure 48
CITP-stacked uraemic sera separation
by CZE 26
Peaks (tentative): 1 = huppuric acid,
2 = p-hydroyhippuric acid, 3 = uric acid
Conditions: 10 mM Mes, histidine, pH 6.05,
0.05 % methyl hydroxyethyl
cellulose, constant current = 35 mA,
l = 25 cm, id = 200 mm,
PTFE capillaries
Zone sharpening can occur upon the addition of a high
concentration of leading and/or trailing electrolytes to the
sample (that is, addition of salt to the sample). An example
of such improvements is illustrated in figure 48. Here, the
sample contains a high concentration of chloride (@110 mM)
in addition to the solutes of interest. The earliest eluting
peaks exhibit over 10 6 plates, significantly more than
described by simple theory. This example also illustrates
how ITP effects can inadvertently occur, especially with
complex samples.
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