Alkoxy Silanes for the Preparation of Silica Based Stationary Phases with Bonded Polar Functional Groups

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Abstract
For preparation of polar bonded phases with alkoxy silanes an activator and a catalyst are required to achieve surface coverages comparable to those obtained with chlorosilanes. For activation a monolayer of water on the silica surface is sufficient. The most active catalyst in many cases has been p-toluene sulfonic acid, however, for silanes with basic groups triethylamine gives better coverages. Silanes with polar groups tend to adsorb also with this group onto the surface thus preventing chemical binding via alkoxy groups. Long time experiences in the preparation of amino phases, anion and cation exchangers and hydrophilic bonded phases for protein analysis are summarized.