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

Modes
CA
a)
liquid chromatography, CE was suggested to hold great
potential for the separation and characterization of polar,
non-volatile environmental samples.
CX
0 5 10 15 20 25
M CX
M 3
4
CA
M
2
M
5
M
1
b)
CZE has also been used for the separation of inorganic ions
and organic acids, which has been traditionally performed
by ion chromatography (figure 33). Indirect UV detection is
necessary due to the lack of chromophores in these species.
Indirect detection is performed using a highly absorbing
species such as chromate or imidazole in the running buffer
and monitoring at the absorbance maximum of that species
(for example, 254 nm for chromate). Solute ions displace
the chromate ions and a decrease in absorbance occurs
when the zones pass the detector region. In order to
decrease the analysis time for the cations shown here, a
cationic surfactant (CTAB) was added to the running buffer
to reverse the EOF toward the cathode. Due to the high
mobility of small ions, however, the EOF is not strong
enough to carry ions migrating in the opposite direction and
thus anions cannot be analyzed simultaneously. In these
small ion determinations, peak shapes are often skewed due
to the conductivity differences between the running buffer
and the ions.
0 10 20 30 40 50
Migration time [min]
Figure 31
a) CZE of Cefixime (CX) and its
metabolites. b) Analysis of human urine
spike with CX and cinnamic acid (CA) 14
Conditions: 50 mM phosphate, pH 6.8,
V = 15 kV, l = 50 cm, L = 72 cm,
id = 50 mm, l = 280 nm
Absorbance
0.0400
0.0200
4-chlorobenzenesulfonate
Figure 32
Analysis of environmentally hazardous
leachates by CZE 15
Conditions: 50 mM borate-boric acid, pH 8.3,
V = 30 kV, i = 33 mA, l = 50 cm,
L = 75 cm, id = 50 mm, l = 280 nm
0.0000
0
10 20 22.25
Time [min]
61