Comparison of enantioseparation of selected benzodiazepine and phenothiazine derivatives on chiral stationary phases based on beta-cyclodextrin and macrocyclic antibiotics

摘要

Enantioselective separation of some phenothiazine and benzodiazepine derivatives was studied on six different chiral stationary phases (CSPs) in HPLC. Selected CSPs, with respect to the structure of the separated compounds, were either based on beta-cyclodextrin chiral selectors - underivatized beta-cyclodextrin and hydroxypropyl ether beta-cyclodextrin, or on macrocyclic antibiotics - vancomycin, teicoplanin, teico-planin aglycone, and ristocetin A. Measurements were carried out in a reversed-phase separation mode. The influence of mobile phase composition on retention and enantioseparation was studied. Benzodiazepines could be enantioresolved with almost all the chiral stationary phases used, except for the vancomycin-bonded CSP. Peak coalescence of oxazepam and lorazepam was observed if separation was carried out at laboratory temperature. Reduced temperature was required in some instances in order to avoid the on-column racemization. Separation systems composed of teicoplanin-bonded CSP and buffer-methanolic or pure methanolic mobile phases were shown to be suitable even for preparative purposes due to high resolution values of the enantiomers, Enantioseparation of phenothiazine derivatives was more difficult to achieve but it was successful, at least partly, also with both types of the CSPs used (except for levomepromazine).