title: Approaches for the coating of capillary columns with highly phenylated stationary phases for high-temperature GC.
abstract: Two highly phenylated tetramethyl-p-silphenylene-diphenylsiloxane copolymers were coated on fused silica capillary columns and used as stationary phases in GC. The copolymers offered new insights into the coating process and column preparation due to their physicochemical properties. The fused silica capillary surface had to be pretreated in various ways to achieve a homogeneous film and a well deactivated surface: etching with ammonium bifluoride; leaching with sodium hydroxide and hydrochloric acid; silylation with tetraphenyldimethyldisilazane and triphenylsilylamine. Droplet formation was observed on tetraphenyldimethyldisilazane silylated surfaces leading to capillary columns with low separation efficiency. The topology of inhomogeneous films was investigated by light microscopy, scanning electron microscopy, and Auger electron spectroscopy. It became apparent that the stationary phase did not form droplets but islands, which are connected by a wetting layer according to the Stranski-Krastanov growth mode. Both copolymers are potential stationary phases for high-temperature GC with promising properties. They offer a higher overall polarity than 75% phenyl, 25% methyl-polysiloxanes in combination with increased thermal stability and reduced bleed levels.
authors.affiliation: Department of Clinical Pharmacology, University School of Medicine, Währinger Gürtel 18-20, 1090 Vienna, Austria. Bernhard.Mayer@univie.ac.at
authors.forename: Bernhard X
authors.initials: BX
authors.lastname: Mayer-Helm
authors.forename: Walfried
authors.initials: W
authors.lastname: Rauter
authors.forename: Georg
authors.initials: G
authors.lastname: Rauchbauer
authors.forename: Christian
authors.initials: C
authors.lastname: Tomastik
authors.forename: Herwig
authors.initials: H
authors.lastname: Bangert