Silica, alumina and aluminosilicates as solid stationary phases in gas chromatography

Silica, alumina and Aluminosilicates of different Si/Al ratios were prepared by conventional precipitation or co-precipitation methods and then subjected to thermal treatment at 800 degrees C. The parent and thermally treated materials were characterized by means of FTIR, SEM and thermal analysis (DTA and TGA) in order to elucidate the main structural properties. Surface textural characteristics were investigated by means of nitrogen adsorption-desorption isotherms at -196 degrees C. Pore size distribution curves indicated the presence of mesopores (10-150 angstrom) exhibiting maxima at 35 angstrom. The maxima were shifted toward higher values by increasing the alumina content. Thermodynamic parameters, DH, DG and DS, were determined by means of inverse gas chromatography using n-hexane as a probe. The untreated and thermally treated materials were tested as solid stationary phases in gas chromatography. The separation efficiency of various non polar and polar compounds was explained in terms of surface texture and thermodynamic parameters. (C) 2011 Production and hosting by Elsevier B.V. on behalf of King Saud University.