Aligned electrospun nanofibers for ultra-thin layer chromatography.

The fabrication and implementation of aligned electrospun polyacrylonitrile (PAN) nanofibers as a stationary phase for ultra-thin layer chromatography (UTLC) is described. The aligned electrospun UTLC plates (AE-UTLC) were characterized to give an optimized electrospun mat consisting of high nanofiber alignment and a mat thickness of ~25 µm. The AE-UTLC devices were used to separate a mixture of ß-blockers and steroidal compounds to illustrate the properties of AE-UTLC. The AE-UTLC plates provided shorter analysis time (~2-2.5 times faster) with improved reproducibility (as high as 2 times) as well as an improvement in efficiency (up to100 times greater) relative to non-aligned electrospun-UTLC (E-UTLC) devices.

Electrospun nanofibrous solid-phase microextraction coatings for preconcentration of pharmaceuticals prior to liquid chromatographic separations.

Electrospun epoxide polymer and carbon nanofiber-based SPME phases were examined for their application to the direct extraction of nonvolatile analytes coupled to liquid chromatography (LC). All of the electrospun nanofiber-coated SPME fibers demonstrated superior extraction efficiencies which were 2-32 times higher than a commercially available SPME fiber, with the electrospun coating processed at 800°C demonstrating the highest extraction efficiency. The carbonized electrospun nanofiber-coated SPME fibers showed no swelling when immersed in a variety of liquids, demonstrating the improved chemical stability these coatings have over traditional polymer-coated SPME fibers, which typically swell during direct extraction. Additionally, these robust coatings exhibit prolonged fiber lifetimes, withstanding up to 100 direct extractions without significant damage or change in nanofiber morphology. The detection limits of the method were found to be 2-3 orders of magnitude lower than those reported when using commercially available polyacrylate (PA) SPME fiber under similar conditions.

Electrospun fibers for solid-phase microextraction.

A method of producing solid-phase microextraction (SPME) fibers based on electrospinning polymers into nanofibrous mats is demonstrated. Using this method the polymer mat is attached to a stainless steel wire without the need of a binder. While applicable to any polymer that can be electrospun, a polymeric negative photoresist, SU-8 2100, is used for this initial study. SPME devices composed of carbon nanofibers are also illustrated by pyrolyzing SU-8 to produce amorphous carbon. Nonpolar compounds, benzene, toluene, ethylbenzene, and o-xylene (BTEX) and polar compounds, phenol, 4-chlorophenol and 4-nitrophenol are extracted under headspace SPME conditions. Extraction efficiencies are compared to commercial polydimethylsiloxane (PDMS), polydimethylsiloxane/divinylbenzene (PDMS/DVB), and polyacrylate (PA) fibers. For both the nonpolar and polar compounds, the carbon nanofiber based phases demonstrated enhanced or comparable (o-xylene only) extraction efficiencies. Distribution constants, K, for benzene on the electrospun fibers are of greater or similar magnitude to those of the compared commercial fibers and increase with carbonization temperature. Finally, the measured detection limits for all the organic compounds are similar to those measured with other SPME gas chromatography-flame ionization detector (GC-FID) methods with a large linear dynamic range (3 orders of magnitude) for quantification.