Functional groups, silica surfaces

The solid sorbents closely resemble to that of the solid stationary phases of liquid chromatography. Bonded silica gels (of reverse phase polarity) with a particle size of between 4 and 100 p.m, allow a percolation of faster flow rate. Other adsorbents, containing graphite or co-polymers such as styrene-divinylbenzene of large functional group bonded surfaces, are more stable in acidic solutions. 

Nowadays, almost all commercially available HPLC stationary phases are also applicable to planar chromatography. In addition to the polar hydroxyl groups present on the surface of native silica, other polar functional groups attached to the silica skeleton can also enter into adsorptive interactions with suitable sample molecules (34). Silica with hydrophilic polar ligands, such as amino, cyano, and diol functions, attached to the silica skeleton by alkyl chains, all of which have been well proven in HPLC, have also been developed for TLC (34). 

Chemically bonded layers are prepared by reacting silica gel with various functionalized organosilane reagents forming siloxane Ssonds with some of the silanol groups originally present on the silica surface (10,23,71-77). Chemically bonded siloxane layers... 

Figure 4.2 Characteristic functional groups present on a silica surface.

Silica or porous glass is usually used as the solid phase in oligonucleotide synthesis. The support is functionalized through an amino group attached to the silica surface. There is a secondary linkage through a succinate ester to the terminal 3 -OH group. 

Figure 2 Functional groups present on the surface of porous, amorphous silica...

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