Document Detail

Effect of temperature on enantiomer separation of oxzepam and lorazepam by high-performance liquid chromatography on a beta-cyclodextrin derivatized bonded chiral stationary phase.
MedLine Citation:
PMID:  15023256     Owner:  NLM     Status:  MEDLINE    
A reversed-phase high-performance liquid chromatography (HPLC) method with beta-cyclodextrin (beta-CD) derivatized as chiral stationary phase is used to directly separate oxazepam (Oxa) and lorazepam (Lor) enantiomers. The effect of temperature on the direct HPLC separation of Oxa and Lor enantiomers is studied for the commercially available beta-CD derivatized bonded chiral stationary phase. Chromatographic peak coalescence, appearing as a plateau between the resolved peaks, is observed at column temperatures of above 13 degrees C. Peak coalescence on the beta-CD derivatized bonded column is attributable to racemization of the Oxa enantiomer. By reducing the column temperature to 13 degrees C, the enantiomeric composition of Oxa and Lor could be determined on the chiral column. This method is expected to be useful for the resolution of 3-hydroxybenzodiazepines. At the same time, the separation mechanism is studied by calculating the thermodynamic parameters. The results reveal that the separation of Oxa and Lor enantiomer is a case of enthalpy-controlled separation, inclusion mechanism does not control the separation. The interaction between Oxa and beta-CD is an additionally strong pi-pi interaction or hydrogen bonding, but that between Lor or beta-CD derivatized is a weak pi-pi interaction or hydrogen bonding.
Hua He; Yang Liu; Cheng Sun; Xiaorong Wang; Chuong Pham-Huy
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of chromatographic science     Volume:  42     ISSN:  0021-9665     ISO Abbreviation:  J Chromatogr Sci     Publication Date:  2004 Feb 
Date Detail:
Created Date:  2004-03-16     Completed Date:  2004-04-22     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0173225     Medline TA:  J Chromatogr Sci     Country:  United States    
Other Details:
Languages:  eng     Pagination:  62-6     Citation Subset:  IM    
State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210093, China.
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MeSH Terms
Anti-Anxiety Agents / isolation & purification*
Chromatography, High Pressure Liquid / methods*
Cyclodextrins / chemistry*
Lorazepam / isolation & purification*
Oxazepam / isolation & purification*
Spectrophotometry, Ultraviolet
Reg. No./Substance:
0/Anti-Anxiety Agents; 0/Cyclodextrins; 0/beta-Cyclodextrins; 604-75-1/Oxazepam; 7585-39-9/betadex; 846-49-1/Lorazepam

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