Chain Order and Mobility of High-Density C18 Phases by Solid-State NMR Spectroscopy and Liquid Chromatography
- 1 December 1996
- journal article
- research article
- Published by American Chemical Society (ACS) in Analytical Chemistry
- Vol. 68 (23) , 4107-4113
- https://doi.org/10.1021/ac9606113
Abstract
C18 phases prepared by different synthetic pathways are examined by solid-state NMR spectroscopy. Silane functionality is clearly indicated by 29Si CP/MAS NMR spectroscopy. Order and mobility of the alkyl chains are investigated with high-speed 1H MAS and 13C CP/MAS NMR spectroscopy. Differences in coverage are monitored by 1H line widths, 13C chemical shifts, 13C cross-polarization constants, and 1H relaxation times in the rotating frame. It is shown that C18 phases prepared by the surface polymerization technique exhibit a more regular surface coverage than sorbents prepared by conventional polymeric synthesis. The findings from solid-state NMR investigations are discussed in the context of liquid chromatography (LC) separations of linear and bulky polycyclic aromatic hydrocarbon (PAH) solutes.Keywords
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