Preparation and characterization of fused-silica capillary columns coated with m-carborane-siloxane copolymers for gas chromatography

The carborane-siloxane copolymers Dexsil 300, a 34.5% bis(dimethylsilyl)-m-carborane-65.5% dimethylsiloxane copolymer, and Dexsil 400, a 24.9% bis(dimethylsilyl)-m-carborane-50.8% dimethyl, 24.3% methylphenylsiloxane copolymer, were coated on fused silica capillary columns and their gas chromatographic properties were evaluated. Their selectivity was evaluated using both Rohrschneider-McReynolds constants and triacylglycerol indices. The bis(dimethylsilyl)in-carborane unit turned out to be equivalent to two dimethylsiloxy units and one half of a diphenylsiloxy unit. The in-carborane unit was found to cause a 1525 K shift in the elution temperature between 120 and 360 degrees C. The working range was from 20 and 0 degrees C to 380 degrees C for Dexsil 300 and Dexsil 400, respectively. The column bleeding levels at 380 degrees C were below 20 and 15 pA for Dexsil 300 and Dexsil 400, respectively.