Surface Characterization of Some Novel Bonded Phase Packing Materials for HPLC Columns Using MAS-NMR Spectroscopy

Abstract

Information on the surface properties of three novel chemically bonded phase packing materials for High performance liquid chromatography (HPLC) were obtained using spectra obtained by solid state cross-polarization (CP) magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopic experiments for the 29 Si, and 13 C nuclei. These packing materials were: Cogent bidentate C18 bonded to type-C silica, hybrid packing materials XTerra MS C18, and XBridge Prep. C18. The spectra obtained using cross-polarization magic angle spinning (CP-MAS) on the Cogent bidentate C18 bonded to type-C silica show the surface to be densely populated with hydride groups (Si-H), with a relative surface coverage exceeding 80%. The hybrid packing materials XTerra and XBridge gave spectra that reveal the silicon atoms to be bonded to organic moieties embedded in the molecular structure of these materials with over 90% of the alkyl silicon atoms found within the completely condensed silicon environments. The hydrolytic stability of these materials were investigated in acidic aqueous solutions at pHs of 7.0 and 3.0, and it was found that while the samples of XTerra and XBridge were not affected by hydrolysis at this pH range, the sample of Cogent lost a significant proportion of its Si-H groups after five days of treatment in acidic aqueous solution.

Facile one pot synthesis of mesoporous organic–inorganic hybrid aluminosilicate spheres with ultra-high aluminium contents and their enhanced adsorption behavior for methylene blue

“…Fig. 4 shows the 29 Si and 27 Al MAS NMR spectra of the template-extracted sample HMAS 1 , the 29 Si NMR spectrum demonstrates a broad peak at À53.6 ppm for the T 2 site (SiC(OH)(OSi) 2 ) or the T 3 site (SiC(OAl)(OSi) 2 ), while the shoulder at À44.7 ppm is probably attributed to the T 1 silicon site (SiC(OH) 2 (OSi)) [36][37][38] (Fig. 4a).…”