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

Modes
Amplitude
2
a)
with a migration time reproducibility of 0.8 % RSD and a peak
area reproducibility of 2.2 % RSD.
1
3, 4
3.3 6.6 9.9 13.2
2
1
3
4
9.9 13.2 16.5 19.8
Time [min]
Figure 38
Separation of closely related peptides
using non-ionic surfactants 18
Peaks: 1 = bradykinin, 2 = luteinizing hormone
releasing hormone, 3 = [val 2 ]-angiotensin III,
4 = angiotensin III, 5 = angiotensin II
Conditions: 250 mM phosphate, pH 7, 80 mM
octyl glucoside (only in B),
E = 250 V/cm, i = 33 mA, l = 70cm,
id = 17 mm, l = 210 nm, aryl
pentafluoro coated capillaries
Figure 39
MEKC forensic drug screen 19
Conditions: 8.5 mM borate, 8.5 mM phosphate,
85 mM SDS, 15 % acetonitrile,
pH 8.5, V = 20 kV, l = 25 cm,
L = 47 cm, id = 50 mm, l = 210 nm
5
b)
5
The use of non-ionic surfactants to enhance selectivity is
illustrated in figure 38. Peaks 3 and 4 are angiotensin III
neuropeptides which differ by a single methyl substitution.
As shown, no resolution of peaks 3 and 4 was obtained by
CZE (figure 38a). Upon addition of 80 mM octyl glucoside the
pair was resolved. Non-ionic (and zwitterionic) surfactants
are advantageous in that they do not dramatically change
the EOF, do not increase the conductivity of the buffer, and
can have little impact on protein structure or activity.
An example of the use of MEKC for the analysis of illicit
drugs for forensic purposes is shown in figure 39. Here, a
phosphate-borate buffer containing SDS and acetonitrile was
employed. This analysis shows that MEKC is applicable to a
large variety of forensic samples. It was especially useful for
those samples that were difficult to analyze by GC, including
phenethylamines, benzodiazapines, ergot alkalids, psilcybin,
and PCP. For LSD and LAMPA, MEKC was thought to be
superior to HPLC, which was usually employed.
Volts
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0
b c d e
f
a
h
g
i
j
a Psilocybin
b Morphine
c Phenobarbital
d Psilocin
e Codeine
f Methaqualone
g LSD
h Heroin
i Amphetamine
m n
k l
o
0 4 8 12 16 20 24 28 32 38 40 44
Time [min]
p
j
k
l
m
n
o
p
q
r
Librium
Cocaine
Methamphetamine
Lorazepam
Diazapam
Fentanyl
PCP
Cannabidiol
D
9
- THC
q
r
68