SPECTROSCOPIC AND CHROMATOGRAPHIC EVALUATION OF CYCLIC SILOXANE BONDED PHASES FOR MICROCOLUMN GAS-CHROMATOGRAPHY OF LOWER HYDROCARBONS

Cyclic organosiloxanes were chemically bonded to silica gels and evalu ated for possible use in microcolumn gas chromatography of light hydro carbons in extraterrestrial atmospheres. DRIFT and solid state NMR spe ctroscopic studies confirmed the bonding of the siloxanes onto the sil ica surface. The surface concentration of the phases, which varied wit h the reactivity of the siloxane bond toward proton attack, were in th e range of 0.31 mu mol m(-2) for octaphenylcyclotetrasiloxane to 2.39 mu mol m(-2) for hexamethylcyclotrisiloxane packings. Of the five colu mns investigated, hexamethylcyclotrisiloxane and pentamethylcyclopenta siloxane bonded phases seem to provide good separation of the test sol utes presumably due to their somewhat higher surface coverage. All the columns gave similar H vs. (u) over bar curves with a shallow and fla t minimum at the optimum region. The phases are thermally stable up to 300 degrees C and allowed fast analysis of C-1-C-4 hydrocarbons under isothermal conditions. (C) 1996 John Wiley & Sons, Inc.