title: Separation of oxazepam, lorazepam, and temazepam enantiomers by HPLC on a derivatized cyclodextrin-bonded phase: application to the determination of oxazepam in plasma.
abstract: The enantioselective high-performance liquid chromatography (HPLC) of three racemic 3-hydroxybenzodiazepines, oxazepam (Oxa), lorazepam (Lor), and temazepam (Tem), is a difficult operation because of the spontaneous chiral inversion in polar solvent. To solve this problem, we have developed an HPLC method based on a chiral Cyclobond I-2000 RSP column, maintained at 12 degrees C, and a reversed mobile phase (acetonitrile in 1% triethylamine acetate buffer, TEAA) at a flow rate of 0.4 ml/min. Peaks were detected by a photodiode-array detector at 230 nm for quantification and by an optical rotation detector for identification of (+) and (-) enantiomers. The results showed that peak resolutions of Oxa, Lor, and Tem enantiomers, analyzed under the same conditions, were 3.2, 2.0, and 1.8, respectively. For the determination of Oxa enantiomers in plasma of rabbits, extraction with diethyl ether at pH 1.5, a polar organic mobile phase, and a Cyclobond I-2000 SP column were used. Other analytical conditions were the same as previously described. Blood samples were immediately cooled at 4 degrees C and centrifuged at 0 degrees C for the collection of plasma. The results showed a difference in plasma S(+)- and R(-)-oxazepam concentrations in rabbits. No racemization of S(+)- or R(-)-Oxa enantiomers, added alone to blank plasma, was observed after extraction and enantioselective HPLC analysis.
authors.affiliation: Laboratory of Toxicology, Faculty of Pharmacy, University of Paris V, 4 avenue de l'Observatoire, 75006 Paris, France. pham.huy.chuong@wanadoo.fr
authors.forename: Chuong
authors.initials: C
authors.lastname: Pham-Huy
authors.forename: Géraldine
authors.initials: G
authors.lastname: Villain-Pautet
authors.forename: He
authors.initials: H
authors.lastname: Hua
authors.forename: Nassima
authors.initials: N
authors.lastname: Chikhi-Chorfi
authors.forename: Hervé
authors.initials: H
authors.lastname: Galons
authors.forename: Marc
authors.initials: M
authors.lastname: Thevenin
authors.forename: Jean-Roger
authors.initials: JR
authors.lastname: Claude
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Warnet
mesh_terms: D000818:Animals; D001570:Benzodiazepinones / Q000032:analysis / Q000737:chemistry / Q000145:classification / Q000302:isolation & purification*; D002851:Chromatography, High Pressure Liquid / Q000295:instrumentation / Q000379:methods*; D003505:Cyclodextrins / Q000032:analysis / Q000097:blood / Q000737:chemistry / Q000145:classification / Q000302:isolation & purification; D008140:Lorazepam / Q000032:analysis / Q000737:chemistry / Q000145:classification / Q000302:isolation & purification*; D009904:Optical Rotation; D010076:Oxazepam / Q000032:analysis / Q000097:blood* / Q000737:chemistry / Q000145:classification / Q000302:isolation & purification*; D011786:Quality Control; D011817:Rabbits; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013237:Stereoisomerism; D013693:Temazepam / Q000032:analysis / Q000737:chemistry / Q000145:classification / Q000302:isolation & purification*
chemical_list: D001570:Benzodiazepinones; D003505:Cyclodextrins; D010076:Oxazepam; D013693:Temazepam; D008140:Lorazepam