Thermal and Hydrothermal Treatment of Silica Gels as Solid Stationary Phases in Gas Chromatography

Silica gel was prepared and treated thermally and hydrothermally and was characterized as solid stationary phase in gas chromatography. The characteristics have been evaluated in terms of polarity, selectivity, and separation efficiencies. These parameters were used to assess the outer silica surface contributions and the degree of surface deactivation brought about by different treatment techniques. The parent silica elutes the paraffinic hydrocarbons with high efficiency of separation and elutes aromatic hydrocarbons with nearly good separation and has bad separation of alcohols. The calcined silica at 500°C and 1000°C has a pronounced effect on the separation of aromatic hydrocarbons compared with the parent silica and hydrothermal treatment of silica. With respect to alcohols separation, the obtained bad separations using treated and untreated silica reflect the little effect of the thermal and hydrothermal treatment on the silica surface deactivation. 1. Introduction Gas chromatography (GC) is now widely used to examine the physicochemical characteristics of many solid and liquid materials. Carefully selected test solutes are injected into the flow of carrier gas and transported over the surface of stationary phase such as silica or others. The retention time and the peak elution profiles of standard solutes affected by interactions between the solutes and stationary phase are used to estimate those interactions [1, 2]. GC can be used for studying the behavior of stationary phase through investigating the interactions between these stationary phases and some solutes from different families [3–5]. Silica gels have long attracted attention since they are widely used and as stationary phase in chromatography, catalyst, extract, filter surface properties covering a wide range of acidity surface reactivity and pore structure [6–8]. The surface of silica gel can be modified easily by physical or chemical treatments leading in each case to different adsorptive properties. These treatments may include calcinations [9], hydrothermal treatment [10], silylation [11–13], and incorporation of organic and inorganic salts or organic compounds [14–17]. Usually, the separation of the mixture requires selective stationary phase, so there are many thousands of these phases, and the novelty of this approach is the silica gel preparation and its treatment with different methods in order to obtain different silica surfaces to cover most chromatographic problems. The purpose of this work is the synthesis and modification of silica gel through thermal and hydrothermal