The Effect of the Reaction Medium on the Coverage Density of C₁₈Chemically Bonded Phase

A wide-pore silica for HPLC (SBET = 360 m2 g−1, D = 20 nm, Vp = 2.1 cm3 g−1) was silanized with n-octadecyl dimethylchlorosilane in the presence of several base activators. It has been found that the density of bonded octadecyl ligands is not only a function of reaction time and temperature, but also depends upon the structure of the organic base used as reaction activator. The reproducible synthesis of silica bearing more than 4/umol m–2 of octadecyl ligands is described.