Ergot alkaloids as novel chiral selectors in capillary electrophoresis

1
Ergot alkaloids as novel chiral selectors in CE
Benno A. Ingelse, Jetse C. Reijenga, Henk A.
Claessens, Frans M. Everaerts and Mirko Flieger
Eindhoven University of Technology, The
Netherlands Academy of Sciences of the Czech
Republic
01/11/96

1
2
Ergot alkaloids
General formula
1-allyl-terguride
3
Experimental

• P/ACE 2200 Beckman Instruments
• Capillary 50 µm, 300/370 mm, PVA-coated
• BGE ?-alanine/acetate allyl-terguride, pH 4.0,
  I50 mM
• UV-detection, 200 nm
• Samples 10-4 M

4
Experimental setup
5
Typical electropherogram using ergot skeletons as
chiral selector
Abs. AU
time minutes
6
Influence of pH on the resolution of some racemic
organic acids
Abs. AU
time minutes
7
Influence of terguride concentration on the
mobility of the analytes
22
mpa1
20
m(eff)
mpa2
18
vm1
16
vm2
14
12
0
5
10
15
20
25
concentration allyl-terguride mM
8
Determination of the Kc-value of vanilmandelic
acid enantiomers
1.40
1.30
µ1/µA
1.20
K
c
1.10
1.00
0
5
10
15
20
25
concentration allyl-terguride (mM)
9
Influence of MeOH on the chiral separation of the
racemic organic acids
Abs. AU
time minutes
10
Influence of terguride concentration on the
mobility of the analytes in 50 MeOH
16
mpa1
14
mpa2
m(eff)
12
vm1
vm2
10
8
0
10
20
30
40
50
60
70
concentration allyl-terguride mM
11
Determination of the Kc-value of
?-methyl-phenylacetic acid enantiomers using MeOH
1.40
1.30
µ1/µA
1.20
K
c
1.10
1.00
0
5
10
15
20
25
concentration allyl-terguride (mM)
12
Full separation of some racemic organic acids
using 25 mg/mL allyl-terguride
Abs. AU
time minutes
13
Selectivity with and without MeOH
tropic acid
mandelic acid
50 MeOH
0 MeOH
50 MeOH
0 MeOH
0.06
0.06
S
S
0.04
0.04
0.02
0.02
0.00
0.00
0
20
40
60
0
20
40
60
Concentration allyl-terguride mM
Concentration allyl-terguride mM
14
Conclusions

• Allyl-terguride has great potential as a chiral
  selector for organic acids
• The dissociated acid forms stereoselective
  complexes with the ergot alkaloid
• Solubility of the ergot-alkaloid in water is
  limited
• Methanol increases solubility
• Methanol influences stereoselectivity