1H 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 1H 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 1H 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 T1 and T1pH relaxation times on temperature and spinning speed.