| Sol-gel capillary microextraction (CME) is a new direction in solvent-free extraction and preconcentration of trace analytes. CME presents significant interest in environmental, pharmaceutical, petrochemical, biomedical, agricultural, food, flavor, and a host of other important areas. Sol-gel CME utilizes advanced material properties of organic-inorganic hybrid sol-gel polymers to perform efficient extraction and enrichment of target analytes from a variety of matrices. In this dissertation, two novel sol-gel coatings were developed for CME: (a) sol-gel benzyl-terminated dendrimer coating, and (b) sol-gel polytetrahydrofuran (poly-THF) coating. A detailed investigation was conducted to evaluate the performance of the newly developed sol-gel coatings in solvent-free extraction of a wide range of polar and nonpolar analytes.; Sol-gel chemistry was used to chemically immobilize dendrimer- and poly-THF-based hybrid organic-inorganic coatings on fused silica capillary inner surface. The sol-gel coatings were created using a coating solution containing a sol-gel active organic component (dendrimer or poly-THF), a sol-gel precursor (methyltrimethoxysilane, MTMOS), a sol-gel catalyst (trifluoroacetic acid, TFA, 5% water) and a deactivating reagent (hexamethyldisilazane, HMDS). Sol-gel reactions were conducted inside a hydrothermally treated fused silica capillary for 60 min. A wall-bonded sol-gel coating was formed via condensation of silanol groups residing on the capillary inner surface with those on the sol-gel network fragments evolving in close vicinity of the capillary walls. Due to the strong chemical bonding with capillary inner walls, these sol-gel coatings showed excellent thermal and solvent stability in CME in hyphenation with gas chromatography (GC). Using a Flame ionization detector (FID), low parts per trillion (ppt) and parts per quadrillion (ppq) level detection limits were achieved in CME-GC for both polar and nonpolar analytes including polycyclic aromatic hydrocarbons (PAHs), aldehydes, ketones, phenols, and alcohols. The sol-gel coatings were found to be effective in carrying out simultaneous extraction of both polar and nonpolar analytes from the same sample.; To our knowledge, two publications resulting from this research [A. Kabir et al. J. Chromatogr. A 1034 (2004) 1-11; A Kabir et al. J. Chromatogr. A 1047 (2004) 1-13] represent the first reports on the development and use of sol-gel dendrimer and sol-gel poly-THF coatings in analytical microextraction. |
