|Title||Ionic liquid-mediated sol-gel sorbents for capillary microextraction and challenges in glass microfabrication|
Three ionic liquids (ILs), trihexyltetradecylphosphonium tetrafluoroborate (TTPT), N-butyl-4-methylpyridinium tetrafluoroborate (BMPT), and 1-methyl-3-octylimidazolium tetrafluoroborate (MOIC), were utilized to prepare sol-gel sorbent coatings. Non-polar polydimethylsiloxane (PDMS) and polar poly(ethylene glycol) (PEG), poly(tetrahydrofuran) (PolyTHF) and bis[(3-methyldimethoxy-silyl)propyl] polypropylene oxide (BMPO) polymers were employed to develop novel ionic liquid-mediated sol-gel hybrid organic-inorganic sorbents. The novel sorbents were first tested as coatings for capillary microextraction off-line hyphenated to gas chromatography. To gain an understanding of the role of the ionic liquids in the sol-gel process, the preconcentration abilities of these novel coatings were investigated for several classes of compounds utilizing CME-GC. This was accomplished by comparing GC peak areas of a series of analytes extracted on the ionic liquid mediated sol-gel CME coatings with that of analogous peak areas obtained on sol-gel coatings prepared without the ionic liquid. The morphology of these coatings was compared using scanning electron microscopy (SEM) imaging data. Overall, the ionic liquid-mediated sol-gel coatings had more porous morphologies than the sol-gel coatings prepared without ionic liquid. The PDMS and BMPO sol-gel coatings prepared with ionic liquid in the sol solution provided enhanced extraction sensitivity reflected in higher preconcentration effects and lower detection limits than the sol-gel coatings prepared without the ionic liquid. The polar IL-mediated BMPO sol-gel sorbent was further investigated by exploring the extraction profile and thermal stability of these coatings. A further application of ionic liquid-mediated sol-gel sorbents could be as stationary phases in a microchip-based separation system. Towards this goal, microfluidic channels were fabricated in glass substrates using microelectromechanical engineering. Spiral and serpentine channels were etched in Pyrex and fused silica wafers using wet and deep reactive ion etching (DRIE) techniques. Microfabrication protocols such as the use of hard mask and etching times were investigated for both techniques. DRIE produced microfluidic channels that had an etch quality that was superior to wet etched channels. Thus, the ultimate microchip-based separation system should by fabricated using DRIE.
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