H-1 MAS NMR spectroscopy of chemically modified silica gels: A fast method to characterize stationary interphases for chromatography

Chemically modified silica gels used as stationary phases in chromatography have been investigated by means of solid-state H-1 magic angle spinning (MAS) NMR spectroscopy. Since the organosilanes are bonded to the surface of the silica gel, their protons are diluted and possess a higher mobility in comparison to protons in pure organic solids. Thereby the usually strong homonuclear dipole-dipole interactions among the protons are reduced and it is possible to obtain well-resolved H-1 NMR spectra of the organic interphases with MAS-only techniques. Effects of temperature and magnetic field strength on the resolution of the spectra are examined as well as the dependence of T-1 and T-1 rho H relaxation times on temperature and spinning speed.