Abstract
The high performance of chemically-modified silica gel packing materials is based on the utilization of pure silica gels. Earlier silica gels used to be made from inorganic silica; however, nowadays, silica gels are made from organic silanes. The surface smoothness and lack of trace metals of new silica gels permits easy surface modifications (chemical reactions) and improves the reproducibility and stability. Sharpening peak symmetry is based on developing better surface modification methods (silylation). Typical examples can be found in the chromatography of amitriptyline for silanol testing and that of quinizarin for trace metal testing. These test compounds were selected and demonstrated sensitive results in the measurement of trace amounts of either silanol or trace metals. Here, we demonstrate the three-dimensional model chemical structures of bonded-phase silica gels with surface electron density for easy understanding of the molecular interaction sites with analytes. Furthermore, a quantitative explanation of hydrophilic and hydrophobic liquid chromatographies was provided. The synthesis methods of superficially porous silica gels and their modified products were introduced.
Highlights
This aim of the review is to explain the properties of the bonded phases
Attaching small nonporous particles on the surface of nonporous core silica gels [104,106]: Nanoparticles in solution are fused to the surface of the nonporous silica core using urea-formaldehyde, and the remaining organics are removed by high temperature treatment [104]
The explanation of the theoretical plate number is the physical selectivity of the stationary phase
Summary
This aim of the review is to explain the properties of the bonded phases. First, definition in liquid chromatography was described using in silico analysis. MIES was changed as the alkyl alcohol was varied up to propyl-phase, especially for ionized benzoic acid, but MIHB was constant This result indicated that an anion may reach a chemically bonded site of silica gel and not be repulsed from the alkyl groups. The selectivity of bonded-phase silica gels was analyzed using the same approach to explain the differences between the hydrophilic, hydrophobic, and ion-exchange mechanisms. The calculated energy values indicated the selectivity of these model phases and the retention mechanisms These compounds were retained at the alkyl-ligands of the bonded-phases by VW interaction, and the polar groups by HB. The addition of MI energy values calculated using a model solvent phase improved the in silico analysis of the retention time of acidic drugs in reversed-phase liquid chromatography [45]
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