New stationary phases of conjugated π-electron systems for HPLC—characterization of structure and dynamics by solid state NMR spectroscopy
✍ Scribed by Ellwanger, Arndt ;Brindle, Rainer ;Albert, Klaus
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 657 KB
- Volume
- 20
- Category
- Article
- ISSN
- 0935-6304
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✦ Synopsis
Abstract
Four new stationary phases for HPLC were prepared by modifying silica gel with a trifrnctional aminoalkyl silane. A conjugated π‐electron system was linked to the amino group either directly or with a carboxylic anhydride as a spacer in between. Characterization and dynamic measurements of the new stationary phases were performed by solid state NMR spectroscopy. The results of the ^29^si and ^13^C CP/MAS techniques were compared with the recently developed ^1^H MAS‐only technique. Despite strong homonuclear dipole‐dipole interactions it was possible to obtain well resolved ^1^H MAS spectra of those stationaru phases with a high degree of crosslinking. Limited mobility of the aromatic ligand fragments is common for all examined stationaryu phases.
The chromatographic properties of the new phases were tested by their ability tio sepatate a mixture of eight PAHS. It could be shown that the π‐π interaction mechanism is responsible for the separation of the eight PAHs, because the elution order of the PAHs did not changem despite the use of both a nonpolar mobile phase (n‐heptane) and a polar mobile phase (methanol/ water mixture).