[Interconversion of stereochemically unstable chiral drugs. Part III: Using beta-cyclodextrin as a chiral stationary phase for HPLC separation of diazepam conformers coupled with an off-line NMR experiment].

Chiral beta-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 beta-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.