A Study On Preparation And Performance Of A Kind Of Chloropropyl-functionalized Hybrid Monolithic Column

The monolithic column has been developing rapidly in recent decades. It attracts more and more attention because of its remarkable advantages over the traditional packed columns, such as larger specific surface area, better permeability, faster mass transfer rate, et al. The monoliths which have been commonly reported so far include three types: organic polymer-based monolith, silica-based monolith and organicinorganic hybrid monolith. It′s most widely used in capillary electrochromatography, and the application in micro/conventional liquid chromatography and gas chromatography can also be found.In this paper, the concept and characteristics of monolithic column and its application in gas chromatography were summarized. Using(3-chloropropyl)-trimethoxysilane and tetraethoxysilane as polymeric monomers, a kind of hybrid monolithic capillary column for gas chromatography was prepared by sol-gel technology. The impact of the preparation conditions on the column formation and performance was evaluated. The thermodynamic characteristics of this hybrid column was analyzed through probe molecules′thermodynamic parameters, and the interaction forces between the probe molecules and stationary phase were analyzed through their linear solvation energy relationship. On this hybrid monolithic capillary column, the separations of a couple of compounds with similar boiling points, light hydrocarbons, fatty alcohols and some substituted-benzenes were carried out.The thermodynamic parameters values of probe molecules revealed that, a good linear correlation(R2>0.99) existed between ln k and 1/T, which means the values of ΔH and ΔS were constants during the chromatographic retention according to the Vanˊt Hoff equation, that is also to say, the interaction forces between the probe molecules and stationary phase were constant; all that above proved an exellent stability of the prepared monolithic column. Meanwhile, the retention of all the probe molecules on this hybrid column was an enthalpy-driven process according to the values of ΔH and ΔS. By analyzing the linear solvation energy relationship between the probe molecules and stationary phase, we knew that the main interaction forces of stationary phase with probe molecules were dispersion, hydrogen-bond and dipole-dipole interaction, and the contribution weakens in turn; the result indicated that the characteristic forces of this hybrid monolithic stationary phase was dispersion > hydrogen-bond acidity > dipolarity/polarizability. In addition, the separation results showed a poor column efficiency since the mixtures separations were off baseline, the peak was broad, and the analysis time was long, but the notable separation of the mixtures with the poor column efficiency indicated a certain practical value of the prepared column, so it is meaningful and necessary to carry out further researches and improvements.