Polytetrahydrofuran-and Dendrimer-Based Novel Sol-Gel Coatings for Capillary Microextraction (CME) Providing Parts Per Trillion (ppt) and Parts Per Quadrillion (ppq) Level Detection Limits in Conjunction With Gas Chromatography and Flame Ionization Detection (FID)

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-THFbased hybrid organic-inorganic coatings on fused silica capillary inner surface. The solgel 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