Stationary phases surface coverage

Each term in Eq. 2.1 is discussed later in the chapter. The surface area of a support is governed by its porosity, the more-porous supports requiring greater amounts of stationary phase for coverage. A photomicrograph of 80/100-mesh Chromsorb W-HP appears in Figure 2.1, where the complex pore network is clearly evident. 

Bonding density (or surface coverage) for a stationary-phase is calculated from the percent carbon loading, substrate surface area, and estimated relative molecular... 

Di- and trifimctional silanes are also used for the preparation of alkyl-modified silicas to be employed as chromatographic sorbents. Under anhydrous reaction conditions, sorbents prepared from these silanes have similar surface coverages and chromatographic behavior to monomeric stationary phases prepared with monofunctional silanes. 

The high surface coverage and near-crystalline structure of SAMs has limited their application as stationary phases in RPLC. Wirth et al. [70,71] have described the preparation of SAM-based chromatographic materials with the use of mixed... 

Ducey, M.W., Jr., Orendorff, C.J., Pemberton, J.E., and Sander, L.C., Structure-function relationships in high density octadecylsilane stationary phases by Raman spectroscopy 1. Effects of temperature, surface coverage and preparation procedure, Anal. Chem., 5576, 2002. 

Gritti, R and Guiochon, G, Adsorption mechanism in reversed-phase liquid chromatography—effect of the surface coverage of a monomeric C-18-sihca stationary-phase, 7. Chromatogr. A, 1115, 142, 2006. 

Lippa, K.A., Sander, L.C., and Mountain, R.D., Molecular dynamics simulations of alkylsilane stationary-phase order and disorder. 1. Effects of surface coverage and bonding chemistry, Anal. Chem., 77, 7852, 2005. 

R stands for the ligand after which the stationary phase is named. A common example is the octadecyl chain, usually abbreviated as Cjg . Due to steric hindrance, not all silanols on a silica surface can react. With modern, high-quality stationary phases, the surface coverage with a Cjg ligand is usually between 3 and 3.5 J,mol/m on a silica surface. 

---