Adsorption, Thermogravimetric, and Chromatographic Studies of Bare Silicas and Silica-Based Octyl Bonded Phases

Abstract

Structural and surface properties of seven chromatographic silica gels were characterized by means of nitrogen adsorption and high-resolution thermogravimetry. The retention of alkyl benzenes was measured using the corresponding commercial octyl-bonded phases. The partition-displacement model was used to evaluate the equilibrium sorption constant and the surface excess of acetonitrile for each octyl phase. Most of the stationary phases studied showed similar sorption properties and, consequently, comparable values of the acetonitrile surface excess. Only for one of the phases studied the surface excess was much higher, and that was attributed to the difference in the silanol coverage of the stationary phase. 1957

Thermal Analysis

“…For this reason, thermal analysis reviews on SiO 2 are treated here. Jaroniec and co-workers focus their research on adsorbent types (182). They characterize many chromatographic forms of silica gel, using TG, adsorption studies, and chromatographic studies.…”

Liquid Chromatography Studies of Acetonitrile Sorption on Silica-Based Octyl Phases

“…[9][10][11]23,24 It should be noticed, however, that even it is true for a given set of solutes noticeable deviations from linearity may occur if the length of bonded phase chains is comparable to that of solutes. For each mobile phase composition a logarithm of the capacity factor lnk' was plotted as a function of the number of carbon atoms in the alkyl chain of solute, n c .…”

“…In turn, the solvent composition of the stationary phase can significantly affect solute retention even in case of the conventional alkyl bonded phases. [8][9][10][11] In this project acetonitrile sorption was studied on two octyl phases of a similar surface coverage synthesized from different silica supports. 5 For instance, in the case of the alkylamide phases the composition of solvents and, consequently, the retentive properties of these phases can be changed significantly in the presence of specific interaction sites in the bonded chains.…”

Adsorption and Thermogravimetric Studies of Mesoporous Silica Coated with Siloxane Polymer

“…Infrared spectroscopy (IR) and solid-state nuclear magnetic resonance (NMR) techniques are commonly used to study the interfacial properties of the aforementioned materials (5,(9)(10)(11)(12)(13)(14)(15)(16). Thermogravimetry, especially its high-resolution option, was also found to be useful for characterization of modified silica gels (17)(18)(19)(20)(21). Gas and vapor adsorption, especially nitrogen adsorption at 77 K, are the techniques of choice for studying not only the surface properties of siliceous adsorbents but also their porous structures (19)(20)(21)(22)(23)(24)(25)(26).…”