Interconversion of Oxazepam Enantiomers During HPLC Separation. Determination of Thermodynamic Parameters

Oxazepam undergoes reversible enantiomerization at ambient temperature. Standard solutions of this compound and extracts from tablets (both with c=0.1 mg/mL) were injected on a chiral HPLC column (Chirobiotic T) at various temperatures (273 K‐313 K, increment 5 K). The mobile phase with the composition MeOH/TEA/Hac (100/0, 1/0, 1) and flow rate 1.0 mL/min were used.1 Both the separation and the interconverson process occurred simultaneously. The various profiles obtained by a UV detector included two peaks (unreacted zone) and a plateau sandwiched between two peaks (reacted zone). These profiles could be explained by on‐column enantiomerization. The unreacted molecule zone on the profile was fused with the reacted molecule zone. The computer assisted peak deconvolution procedure (Origin 7.0 section peak fitting) was used for the determination of peak areas in peak clusters. The deconvolution of experimentally obtained chromatograms enabled the resolved and determined areas of each zones. As follo...