Ion desorption efficiency and internal energy transfer in polymeric electrospun nanofiber-based surface-assisted laser desorption/ionization mass spectrometry.

The understanding of the desorption mechanism in surface-assisted laser desorption/ionization (SALDI) remains incomplete because there are numerous types of SALDI materials with a broad range of physical and chemical properties, many of which impact the ultimate analytical performance in terms of signal generation. In this study, the chemical thermometer molecule, benzylpyridinium chloride, is applied to investigate the desorption process of SALDI using electrospun nanofibrous polymer and polymer composite substrates. The ion desorption efficiency was inversely related to the ion internal energy, which could not be fully explained by a thermal desorption mechanism.

Separation and characterization of KRas proteins and tryptic peptides using enhanced-fluidity liquid chromatography tandem mass spectrometry.

Enhanced-fluidity, reversed-phase liquid chromatography was developed using custom instrumentation for separation and characterization of intact KRas proteins and tryptic peptides. The KRas, HRas and NRas function as GDP-GTP regulated binary switches in many signalling pathways, and mutations in Ras proteins are frequently found in human cancers and represent poor prognosis markers for patients. Mutations of the KRas isoform constitute some of the most common aberrations among all human cancers and intensive drug discovery efforts have been directed toward targeting the KRas protein.

Enhanced-Fluidity Liquid Chromatography-Mass Spectrometry for Intact Protein Separation and Characterization.

Recent advances in the analysis of proteins have increased the demand for more efficient techniques to separate intact proteins. Enhanced-fluidity liquid chromatography (EFLC) involves the addition of liquefied CO to conventional liquid mobile phases. The addition of liquefied CO increases diffusivity and decreases viscosity, which inherently leads to a more efficient separation.

Separation of PEGylated Gold Nanoparticles by Micellar Enhanced Electrospun Fiber Based Ultrathin Layer Chromatography.

Gold nanoparticles (AuNPs) are of great interest in many fields, especially in biomedical applications. Thiol terminated polyethylene glycol (PEG) is the most widely used polymer to increase the biocompatibility of nanoparticle therapeutics. Herein, a rapid method for separation and characterization of PEGylated AuNPs on an ultrathin layer chromatographic (UTLC) plate using electrospun polyacrylonitrile (PAN) nanofibers as the stationary phase is described.

Enhanced fluidity liquid chromatography of inulin fructans using ternary solvent strength and selectivity gradients.

The value of exploring selectivity and solvent strength ternary gradients in enhanced fluidity liquid chromatography (EFLC) is demonstrated for the separation of inulin-type fructans from chicory. Commercial binary pump systems for supercritical fluid chromatography only allow for the implementation of ternary solvent strength gradients which can be restrictive for the separation of polar polymeric analytes. In this work, a custom system was designed to extend the capability of EFLC to allow tuning of selectivity or solvent strength in ternary gradients.

Protein separations using enhanced-fluidity liquid chromatography.

Enhanced-fluidity liquid chromatography (EFLC) methods using methanol/HO/CO and hydrophilic interaction liquid chromatography (HILIC) were explored for the separation of proteins and peptides. EFLC is a separation mode that uses a mobile phase made of conventional solvents combined with liquid carbon dioxide (CO) in subcritical conditions. The addition of liquid CO enhances diffusivity and decreases viscosity while maintaining mixture polarity, which typically results in reduced time of analysis.

Electrospun Nafion-Polyacrylonitrile nanofibers as an ion exchange ultrathin layer chromatographic stationary phase.

An ion-exchange method to separate charged biomolecules on ultrathin layer chromatographic (UTLC) plates using electrospun Nafion-Polyacrylonitrile (PAN) nanofibers as the stationary phase is described. Sulfonate groups on Nafion provide the ion-exchange sites. The addition of PAN (a higher molecular weight polymer than Nafion) was used to facilitate the nanofiber formation process using electrospinning.

Surface-assisted laser desorption/ionization time-of-flight mass spectrometry of small drug molecules and high molecular weight synthetic/biological polymers using electrospun composite nanofibers.

Polyacrylonitrile/Nafion®/carbon nanotube (PAN/Nafion®/CNT) composite nanofibers were prepared using electrospinning. These electrospun nanofibers were studied as possible substrates for surface-assisted laser desorption/ionization (SALDI) and matrix-enhanced surface-assisted laser desorption/ionization time-of-flight mass spectrometry (ME-SALDI/TOF-MS) for the first time in this paper. Electrospinning provides this novel substrate with a uniform morphology and a narrow size distribution, where CNTs were evenly and firmly immobilized on polymeric nanofibers.

Gradient separation of oligosaccharides and suppressing anomeric mutarotation with enhanced-fluidity liquid hydrophilic interaction chromatography.

Enhanced fluidity liquid chromatography using the hydrophilic interaction retention mechanism (EFLC-HILIC) is studied as an alternative separation mode for analyzing oligosaccharides and other sugars. These carbohydrates, which are important for the study of foods and biological systems, are difficult to comprehensively profile and either require a non-green, expensive solvent (i.e.

Gradient enhanced-fluidity liquid hydrophilic interaction chromatography of ribonucleic acid nucleosides and nucleotides: A "green" technique.

A "green" hydrophilic interaction liquid chromatography (HILIC) technique for separating the components of mixtures with a broad range of polarities is illustrated using enhanced-fluidity liquid mobile phases. Enhanced-fluidity liquid chromatography (EFLC) involves the addition of liquid CO2 to conventional liquid mobile phases. Decreased mobile phase viscosity and increased analyte diffusivity results when a liquefied gas is dissolved in common liquid mobile phases.

Enhanced-fluidity liquid chromatography using mixed-mode hydrophilic interaction liquid chromatography/strong cation-exchange retention mechanisms.

The potential of enhanced-fluidity liquid chromatography, a subcritical chromatography technique, in mixed-mode hydrophilic interaction/strong cation-exchange separations is explored, using amino acids as analytes. The enhanced-fluidity liquid mobile phases were prepared by adding liquefied CO to methanol/water mixtures, which increases the diffusivity and decreases the viscosity of the mixture. The addition of CO to methanol/water mixtures resulted in increased retention of the more polar amino acids.

Homogeneous edge-plane carbon as stationary phase for reversed-phase liquid chromatography.

Carbon stationary phases have been widely used in HPLC due to their unique selectivity and high stability. Amorphous carbon as a stationary phase has at least two sites of interaction with analytes: basal-plane and edge-plane carbon sites. The polarity and adsorptivity of the two sites are different.

Development of a new separation media using ultra-thin glassy carbon film modified silica.

A self-polymerizable octatetrayne, 1,8-dialdehydebenzyl-1,3,5,7-octatetrayne, is synthesized and covalently attached to an amino-functionalized surface of silica particles. The silica particles with a monolayer coverage of octatetrayne were then thermally processed to various final temperatures of 200, 400 and 700°C. The amino-functionalization, covalent attachment of octatetrayne and thermal process of silica particles were monitored by scanning electron microscopy (SEM), infrared (IR) spectroscopy and thermogravimetric analysis (TGA).

Planar electrochromatography using an electrospun polymer nanofiber layer.

Electrospun polymer nanofiber stationary phases were examined for their application to planar electrochromatography (PEC). Separations were performed on polyacrylonitrile nanofiber ultra-thin-layer chromatography (UTLC) plates in 1-2 min using a ternary mobile phase. The influences of buffer concentration and pH, ratio of organic modifier, and development time on analyte migration distances were studied.

Silica-based nanofibers for electrospun ultra-thin layer chromatography.

Nanofibrous silica-based stationary phases for electrospun ultra-thin layer chromatography (E-UTLC) are described. Nanofibers were produced by electrospinning a solution of silica nanoparticles dispersed in polyvinylpyrrolidone solutions to create composite silica/polymer nanofibers. Stationary phases were created from as-spun nanofibers, or the nanofibers were heated either to crosslink the polyvinylpyrrolidone or to calcine and selectively remove the polymer.

Carbon nanotube and carbon nanorod-filled polyacrylonitrile electrospun stationary phase for ultrathin layer chromatography.

The application of carbon nanotube or nanorod/polyacrylonitrile (PAN) composite electrospun nanofibrous stationary phase for ultrathin layer chromatography (UTLC) is described herein. Multi-walled carbon nanotubes (MWCNTs) and edge-plane carbon (EPC) nanorods were prepared and electrospun with the PAN polymer solution to form composite nanofibers for use as a UTLC stationary phase. The analysis of laser dyes demonstrated the feasibility of utilizing carbon nanoparticle-filled electrospun nanofibers as a UTLC stationary phase.

Electrospun nanofibers as substrates for surface-assisted laser desorption/ionization and matrix-enhanced surface-assisted laser desorption/ionization mass spectrometry.

Electrospun polymeric nanofibers (polyacrylonitrile, poly(vinyl alcohol), and SU-8 photoresist) and carbon nanofibers pyrolyzed to final temperatures of 600, 800, and 900 °C were used as substrates for surface-assisted laser desorption/ionization (SALDI) and matrix-enhanced surface-assisted laser desorption/ionization (ME-SALDI) analyses. Sample preparation of polymeric analytes using the electrospun target plate for SALDI analysis is simple and fast. Signal enhancements for poly(ethylene glycol) were noted with nanofibrous carbon substrates compared to those obtained with commercially available stainless steel plates when no organic matrix is used.

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 β-blockers and steroidal compounds to illustrate the properties of AE-UTLC.

Electrospun polyvinyl alcohol ultra-thin layer chromatography of amino acids.

Electrospun polyvinyl alcohol (PVA) ultrathin layer chromatographic (UTLC) plates were fabricated using in situ crosslinking electrospinning technique. The value of these ULTC plates were characterized using the separation of fluorescein isothiocyanate (FITC) labeled amino acids and the separation of amino acids followed visualization using ninhydrin. The in situ crosslinked electrospun PVA plates showed enhanced stability in water and were stable when used for the UTLC study.

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.

Characterization of enhanced-fluidity liquid hydrophilic interaction chromatography for the separation of nucleosides and nucleotides.

Hydrophilic interaction chromatography (HILIC) is a liquid chromatographic separation mechanism commonly used for polar biological molecules. The use of enhanced-fluidity liquid chromatography (EFLC) with mixtures of methanol/water/carbon dioxide is compared to acetonitrile/water mobile phases for the separation of nucleosides and nucleotides under HILIC conditions. Enhanced-fluidity liquid chromatography involves using common mobile phases with the addition of substantial proportions of a dissolved gas which provides greater mobile phase diffusivity and lower viscosity.

Separation of poly-3-hydroxyvalerate-co-3-hydroxybutyrate through gradient polymer elution chromatography.

Polyhydroxyalkanoates are biodegradable polyesters produced by bacteria that can have a wide distribution in molecular weight, composition of monomers, and functionalities. This large distribution often leads to unpredictable physical properties making commercial applications challenging. To improve polymer homogeneity and obtain samples with a clear set of physical characteristics, poly-3-hydroxyvalerate-co-3-hydroxybutyrate copolymers were fractionated using gradient polymer elution chromatography (GPEC) as opposed to extensively used bulk fractionation.

High-sensitivity TFA-free LC-MS for profiling histones.

The analysis of proteins by RPLC commonly involves the use of TFA as an ion-pairing agent, even though it forms adducts and suppresses sensitivity. The presence of adducts can complicate protein molecular weight assignment especially when protein isoforms coelute as in the case of histones. To mitigate the complicating effects of TFA adducts in protein LC-MS, we have optimized TFA-free methods for protein separation.

Enhanced fluidity liquid chromatography for hydrophilic interaction separation of nucleosides.

The application of enhanced fluidity liquid (EFL) mobile phases to improving isocratic chromatographic separation of nucleosides in hydrophilic interaction liquid chromatography (HILIC) mode is described. The EFL mobile phase was created by adding carbon dioxide to a methanol/buffer solution. Previous work has shown that EFL mobile phases typically increase the efficiency and the speed of the separation.

Electrospun glassy carbon ultra-thin layer chromatography devices.

The development and application of electrospun glassy carbon nanofibers for ultra-thin layer chromatography (UTLC) are described. The carbon nanofiber stationary phase is created through the electrospinning and pyrolysis of SU-8 2100 photoresist. This results in glassy carbon nanofibers with diameters of approximately 200-350 nm that form a mat structure with a thickness of approximately 15 microm.