hide
Free keywords:
-
Abstract:
New types of silanization reagents for small-particle silica packing materials and a solventless vacuum technique for carrying out the reaction were tested with the aim of conveniently achieving a more complete reaction of the silanol groups. Materials for bonded-phase chromatography with better quality and reproducibility were obtained.
In a second series of experiments we attempted to fix monomeric and oligomeric siloxanes and also certain unsaturated hydrocarbons on either unsilanized or presilanized materials by cross-linking reactions with γ-radiation or peroxides. With the presilanized materials of the Si-O-Si(CH3)3 type we obtained better surface deactivation and fixation of the siloxane oligomers on the surface alkylsilyl groups by the cross-linking reaction.
All silicas should be examined for particle size and structure before and after chemical treatment and analysed for carbon content in bulk and in the surface layer, for permeability and for tailing behaviour after packing of a column. Surface area determinations are also advisable. Chromatographic measurements for efficiency and polarity (selectivity) gave information about the practical value of these materials.
