ABSTRACT
Most chromatographic stationary phases are silica-based. The shapes of silica surfaces are basically unknown. The only method that allows direct measurement of the outer surface shape is atomic force microscopy. Silica-based adsorbents exhibit outstanding mechanical resistance and can provide exceptional efficiency; ultrapure silicas are now available. The specific surface area usually ranges from 120 to 450 m2/g and pore diameters from 60 to 150 Å; the specific pore volume (volumes of all pores in 1 g adsorbent) is 0.5 to 1.2 ml/g.
