SOL-GEL COLUMN TECHNOLOGY FOR SINGLE-STEP DEACTIVATION, COATING, AND STATIONARY-PHASE IMMOBILIZATION IN HIGH-RESOLUTION CAPILLARY GAS-CHROMATOGRAPHY

A sol-gel chemistry-based novel approach to column technology for high -resolution capillary gas chromatography is described that effectively combines surface treatment, deactivation, coating, and stationary pha se immobilization into a single step. In the conventional approach, th ese operations are carried out in separate steps that make column fabr ication a time-consuming job. In the new approach, a cleaned fused sil ica capillary is filled with a sol solution of appropriate composition , and sol-gel reactions are allowed to go on inside the capillary for a controlled period, typically 15-60 min. A wall-bonded coating result s due to condensation of the surface silanol groups with the sol-gel n etwork evolving in their vicinity, Because of the direct chemical bond ing to fused silica substrates, sol-gel coatings possess significantly higher thermal stability than conventional coatings. This is especial ly important for thick and/or polar stationary phase coatings that are difficult to immobilize. Scanning electron microscopic studies reveal ed that sol-gel coatings were characterized by roughened surfaces, pro viding a number of chromatographic advantages, including higher surfac e area and faster mass transfer kinetics. Sol-gel column technology do es not require any free radical crosslinking procedures for stationary phase immobilization and easily avoids any undesirable changes in the stationary phase properties that might be associated with the cross-l inking reactions used in conventional technology. Sol-gel-coated poly( dimethylsiloxane) and Ucon columns provided efficient separations for analytes from a wide polarity range, including free fatty acids, pheno lic compounds, amines, aldehydes, ketones, alcohols, and diols that ar e prone to peak tailing due to adsorptive interactions with the column walls, This suggests excellent quality of column deactivation, The ne w technology provided at least a 10-fold reduction in column preparati on time. The sol-gel approach is universal in nature and can be effect ively applied to a wide range of microcolumn separation techniques.