Interconversion of Stereochemically Unstable Chiral Drugs
Part III: Using ß-Cyclodextrin as a Chiral Stationary Phase for HPLC Separation of Diazepam
Conformers Coupled with an Off-line NMR Experiment
FEDURCOVÁ A.1, LEHOTAY J.1, LIPTAJ T.1, PRÓNAYOVÁ N.1, ČIŽMÁRIK J.2
1Slovenská technická univerzita v Bratislave, Fakulta chemickej a potravinárskej technológie, Ústav analytickej chémie, SR 2Farmaceutická fakulta Univerzity Komenského v Bratislave, Katedra farmaceutickej chémie, SR
Chiral ß-cyclodextrin was used to separate diazepam conformers. Several mobile phases of the composition
acetonitrile/acetate buffer 200 mmol/l (pH=3.3, 5.5, 6.5) were employed for this purpose. As follows, the
influence of addition of chiral ß-cyclodextrin to the mobile phase on diazepam separation was studied. The
interconversion was a concurrence process of separation, resulting from stereolability of the diazepam molecule.
The influences of temperature, flow rate, pH, and ionic strength of the mobile phase on interconversion and
chromatographic parameters (retention factor and selectivity coefficient) were studied. Complementary off-line
NMR measurements were carried out with the goal to confirm the structure of diazepam in the presence of an
acid mobile phase.
interconversion and separation – diazepam – HPLC – NMR