Preparation and characterization - including in situ Small Angle X-Ray Scattering - of gas chromatographic capillary columns with mesoporous silica thin films as stationary phases

In this study the preparation of various mesoporous silica thin films as new stationary phases for gas chromatography (GC) columns is presented. The synthesis was performed inside capillaries via a sol-gel process using a templating route. The as-obtained columns were found to be highly efficient for the fast separation of light n-alkanes (C1-C5) mixture; these columns exhibiting a normalized retention 30 times higher than that of a commercially available silica column used as standard. A particular effort was directed towards the characterization of the stationary phase physical features: thin film inspection by Scanning Electron Microscopy and, for the first time to our knowledge, in situ SAXS characterization using synchrotron radiation were used to study the impact of the pore-network structuration on the GC properties. Worm-like, cubic and hexagonal phases were observed for specific preparation conditions. Unexpectedly, the normalized retention relative to film thickness appeared higher with disordering of the pores network.