Retention mechanism study of imidazole derivatives on a beta-cyclodextrin-bonded stationary phase. Thermal analysis contributions.
Anal Chem
; 70(14): 2819-26, 1998 Jul 15.
Article
in En
| MEDLINE
| ID: mdl-9684543
ABSTRACT
The high-performance liquid chromatography retention mechanism of a series of six imidazole derivatives was investigated over a wide range of mobile-phase compositions, pH, and column temperatures using a beta-cyclodextrin (beta-CD)-bonded chiral stationary phase. Thermodynamic constants for the transfer of a solute from the mobile to the beta-CD stationary phase were determined. Different van't Hoff plot shapes were observed with mobile-phase pH values, indicating a change in the retention mechanism. Enthalpy-entropy compensation revealed that the solute retention mechanism was independent of the compound molecular structure, the same at pH 7 and 7.5, but changed at pH 6.5, 8, and 8.5. Differential scanning calorimetry and thermogravimetric analysis were used to show different thermal features for the beta-CD stationary phase at pH 6.5, 8, and 8.5 and at pH 7 and 7.5. A new theory was presented to explain the beta-CD cavity structure balance between an ordered and disordered state. Variations of column temperature and mobile-phase pH tend to cause this phase transition between these two states, explaining the thermodynamic constant variations with pH and temperature.
Search on Google
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Cyclodextrins
/
Beta-Cyclodextrins
/
Imidazoles
Language:
En
Journal:
Anal Chem
Year:
1998
Document type:
Article
Affiliation country:
France