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Jentaie Shiea - One of the best experts on this subject based on the ideXlab platform.

  • direct protein detection from biological media through Electrospray assisted laser desorption ionization mass spectrometry
    Journal of Proteome Research, 2006
    Co-Authors: Minzong Huang, Hsiujung Hsu, Jenyih Lee, Jingyueh Jeng, Jentaie Shiea
    Abstract:

    We report here using a novel technology-Electrospray-assisted laser desorption ionization (ELDI)/mass spectrometry-for the rapid and sensitive detection of the major proteins that exist in dried biological fluids (e.g., blood, tears, saliva, serum), bacterial cultures, and tissues (e.g., porcine liver and heart) under ambient conditions. This technique required essentially no sample pretreatment. The proteins in the samples were desorbed using a pulsed nitrogen laser without the assistance of an organic matrix. The desorbed protein molecules were then post-ionized through their fusion into the charged solvent droplets produced from the Electrospray of an acidic methanol solution; Electrospray ionization (ESI) proceeded from the newly formed droplets to generate the ESI-like protein ions. This new ionization approach combines some of the features of Electrospray ionization with those of matrix-assisted laser desorption ionization (MALDI), that is, sampling of a solid surface with spatial resolution, generating ESI-like mass spectra of the desorbed proteins, and operating under ambient conditions.

  • Electrospray assisted laser desorption ionization mass spectrometry for direct ambient analysis of solids
    Rapid Communications in Mass Spectrometry, 2005
    Co-Authors: Jentaie Shiea, Minzon Huang, Chenghui Yuan, Iwona B Beech, Jan Sunner
    Abstract:

    A new method of Electrospray-assisted laser desorption/ionization (ELDI) mass spectrometry, which combines laser desorption with post-ionization by Electrospray, was applied to rapid analysis of solid materials under ambient conditions. Analytes were desorbed from solid metallic and insulating substrata using a pulsed nitrogen laser. Post-ionization produced high-quality mass spectra characteristic of Electrospray, including protein multiple charging. For the first time, mass spectra of intact proteins were obtained using laser desorption without adding a matrix. Bovine cytochrome c and an illicit drug containing methaqualone were chosen in this study to demonstrate the applicability of ELDI to the analysis of proteins and synthetic organic compounds.

  • sequential Electrospray analysis using sharp tip channels fabricated on a plastic chip
    Analytical Chemistry, 2001
    Co-Authors: Chenghui Yua And, Jentaie Shiea
    Abstract:

    A disposible plastic (poly(methyl methacrylate)) chip containing eight open channels (375 μm in width, 300 μm in depth, 1.25 cm in length) capable of performing sequential Electrospray analysis is described. The channels were constructed by simply cutting the plastic chip with a sharp knife. One end of each channel was fabricated to a sharp end, while the other was connected to a sample well. The high voltage required for Electrospray was introduced into the sample solution (70% methanol/water) via a copper electrode inserted in the sample well. The solution in the sample well was continuously drawn to the sharp end of the channel by capillary action and by applying the Electrospray voltage at the sample reservoir. A stable and fine Taylor cone was observed at the exit of the channel. Chemical modification on the surface of the channel was not required to decrease wettability. The octagonal plastic chip allowed sequential Electrospray analyses of eight samples. The technique was also shown to be useful in...

  • generation of Electrospray from a solution predeposited on optical fibers coiled with a platinum wire
    Journal of the American Society for Mass Spectrometry, 2000
    Co-Authors: Chihpin Kuo, Chenghui Yuan, Jentaie Shiea
    Abstract:

    This study examines the feasibility of generating Electrospray directly from the tip of two optical fibers bound together with Teflon tape. This approach does not require a capillary and syringe pump. The Electrospray source is simply constructed by coiling the two optical fibers with a platinum (Pt) wire. The optical fibers extend beyond the Pt coil for approximately 1 cm. The sample solution is predeposited on the Pt coil by a micropipette. As the high voltage required for Electrospray is applied to the coil, the sample solution moves along the grooves between the two optical fibers. A stable Electrospray is subsequently generated at the tip of the fibers. The mass spectra of insulin, lysozyme, and ubiquitin are exactly the same as those obtained by conventional Electrospray using a capillary and syringe pump. Rapid determination of the active ingredient in a tablet by this technique is demonstrated.

John P W Stark - One of the best experts on this subject based on the ideXlab platform.

  • the influence of geometry on the flow rate sensitivity to applied voltage within cone jet mode Electrospray
    Journal of Applied Physics, 2012
    Co-Authors: Charles Ryan, Katherine L Smith, John P W Stark
    Abstract:

    This work investigates in greater detail than in previous studies the effect of geometry on the relationship between emitted flow rate and applied potential difference in cone-jet mode Electrospray systems. The magnitude of the flow rate to voltage relationship is demonstrated to be sensitive to numerous geometric parameters. An explanation of this variation is offered; it is demonstrated that in the cone-jet mode of operation the change of flow rate with the applied extraction voltage is due to the change in electric field at the tip of the emitter. By a finite element method simulation of the assumed electrostatic process the analysis is further extended to include all geometric parameters. The results outlined show the change of flow rate with applied voltage in cone-jet mode Electrospray can be significant. This dependence will, under some conditions, have a considerable effect on the Electrospray flow rate, and consequently current and droplet size. This has implications on Electrospray applications involving the use of the applied voltage to extract the sprayed solution, including nano-Electrospray mass spectrometry techniques and some forms of electrospinning.

  • the sensitivity of volumetric flow rate to applied voltage in cone jet mode Electrospray and the influence of solution properties and emitter geometry
    Physics of Fluids, 2006
    Co-Authors: Katharine Smith, Matthew S Alexander, John P W Stark
    Abstract:

    A high accuracy online flow rate measurement system has been used to demonstrate the effect of applied voltage, Vapp, on the volumetric flow rate, Q, through an Electrospray system. Several solutions of the organic solvents ethylene and triethylene glycols doped with sodium iodide to give varying conductivities in the range of 0.0025–0.23S∕m have been sprayed. It was established for the first time that solution conductivity has no appreciable effect on the sensitivity of flow rate to applied voltage in the cone-jet mode of Electrospray. However, it appears that even when the hydraulic resistance is taken into account, the sensitivity of flow rate as controlled by the applied voltage is additionally related to the emitter exit geometry. These findings are of particular importance to both spacecraft propulsion and Electrospray mass spectrometry technologies and suggest careful emitter geometry design considerations will lead to greater control over Electrospray properties.

  • voltage effects on the volumetric flow rate in cone jet mode Electrospraying
    Journal of Applied Physics, 2006
    Co-Authors: Katharine Smith, Matthew S Alexander, John P W Stark
    Abstract:

    Electrospray data collected demonstrate the detailed dependence of volumetric flow rate through an Electrospray system upon the applied voltage. The sensitivity of nominal flow rate to applied voltage was found to be higher for lower nominal flow rates. For a volumetric flow rate ∼4nL∕s a 25% change in flow rate per kilovolt was recorded over a cone-jet mode stability range spanning ∼1.5kV. This volumetric flow rate voltage sensitivity holds particular significance for potential colloid Electrospray propulsion systems, which operate at or near minimum flow rate conditions. Analysis is presented to show that the change in flow rate due to change in voltage cannot be ascribed to evaporation from the meniscus as has been suggested by others.

Himanshu Mishra - One of the best experts on this subject based on the ideXlab platform.

  • reply to the comment on the chemical reactions in Electrosprays of water do not always correspond to those at the pristine air water interface by a j colussi and s enami chem sci 2019 10 doi 10 1039 c9sc00991d
    Chemical Science, 2019
    Co-Authors: Adair Gallo, Andreia S F Farinha, Abdulhamid Emwas, Adriano Santana, Robert J Nielsen, William A Goddard, Himanshu Mishra
    Abstract:

    The air–water interface serves as a crucial site for numerous chemical and physical processes in environmental science and engineering, such as cloud chemistry, ocean-atmosphere exchange, and wastewater treatment. The development of “surface-selective” techniques for probing interfacial properties of water therefore lies at the forefront of research in chemical science. Recently, researchers have adapted Electrospray ionization mass spectrometry (ESIMS) to generate microdroplets of water to investigate interfacial phenomena at thermodynamic equilibrium. In contrast, using a broad set of experimental and theoretical techniques, we found that Electrosprays of water could facilitate partially hydrated (gas-phase) ions (e.g., H3O+·(H2O)2) to drive/catalyze chemical reactions that are otherwise not possible to accomplish by purely interfacial effects (e.g., enhanced water–hydrophobe surface area) (Chem. Sci., 2019, 10, 2566). Thus, techniques exploiting Electrosprays of water cannot be relied upon as generalized surface-selective platforms. Here, we respond to the comments raised by Colussi & Enami (Chem. Sci., 2019, 10, DOI: 10.1039/c9sc00991d) on our paper.

  • the chemical reactions in Electrosprays of water do not always correspond to those at the pristine air water interface
    Chemical Science, 2019
    Co-Authors: Adair Gallo, Andreia S F Farinha, Miguel Dinis, Abdulhamid Emwas, Adriano Santana, Robert J Nielsen, William A Goddard, Himanshu Mishra
    Abstract:

    The recent application of Electrosprays to characterize the air-water interface, along with the reports on dramatically accelerated chemical reactions in aqueous Electrosprays, have sparked a broad interest. Herein, we report on complementary laboratory and in silico experiments tracking the oligomerization of isoprene, an important biogenic gas, in Electrosprays and isoprene-water emulsions to differentiate the contributions of interfacial effects from those of high voltages leading to charge-separation and concentration of reactants in the Electrosprays. To this end, we employed Electrospray ionization mass spectrometry, proton nuclear magnetic resonance, ab initio calculations and molecular dynamics simulations. We found that the oligomerization of isoprene in aqueous Electrosprays involved minimally hydrated and highly reactive hydronium ions. Those conditions, however, are non-existent at pristine air-water interfaces and oil-water emulsions under normal temperature and pressure. Thus, Electrosprays should be complemented with surface-specific platforms and theoretical methods to reliably investigate chemistries at the pristine air-water interface.

Richard D. Smith - One of the best experts on this subject based on the ideXlab platform.

  • elastomeric microchip Electrospray emitter for stable cone jet mode operation in the nanoflow regime
    Analytical Chemistry, 2008
    Co-Authors: Ryan T Kelly, Keqi Tang, Daniel Irimia, Mehmet Toner, Richard D. Smith
    Abstract:

    Despite widespread interest in combining laboratory-on-a-chip technologies with mass spectrometry (MS)-based analyses, the coupling of microfluidics to Electrospray ionization (ESI)-MS remains challenging. We report a robust, integrated poly(dimethylsiloxane) microchip interface for ESI-MS using simple and widely accessible microfabrication procedures. The interface uses an auxiliary channel to provide electrical contact for the stable cone-jet Electrospray without sample loss or dilution. The electric field at the channel terminus is enhanced by two vertical cuts that cause the interface to taper to a line rather than to a point, and the formation of a small Taylor cone at the channel exit ensures subnanoliter postcolumn dead volumes. Cone-jet mode Electrospray was demonstrated for up to 90% aqueous solutions and for extended durations. Comparable ESI-MS sensitivities were achieved using both microchip and conventional fused silica capillary emitters, but stable cone-jet mode Electrosprays could be established over a far broader range of flow rates (from 50-1000 nL/min) and applied potentials using the microchip emitters. This attribute of the microchip emitter should simplify Electrospray optimization and make the stable Electrospray more resistant to external perturbations.

  • generation of multiple Electrosprays using microfabricated emitter arrays for improved mass spectrometric sensitivity
    Analytical Chemistry, 2001
    Co-Authors: Keqi Tang, Yuehe Lin, Dean W Matson, Taeman Kim, Richard D. Smith
    Abstract:

    Arrays of microElectrospray emitters were fabricated on polycarbonate substrates using a laser etching technique. Stable multiElectrosprays were successfully generated in the liquid flow rate range relevant to mass spectrometric applications. Comparison of Electrosprays generated from the microfabricated emitter array and conventional fused-silica capillaries showed similar spray characteristics and reliability. Higher total Electrospray ion currents were observed as the number of Electrosprays increased at a given total liquid flow rate. Consistent with the theoretical prediction, the total spray current at a constant total liquid flow rate was shown experimentally to be approximately proportional to the square root of the number of Electrosprays. It is further projected that when total flow rate is optimized the maximum achievable total current will be proportional to the number of emitters. Evaluation of the multiElectrospray device using a triple quadrupole mass spectrometer showed a factor of 2-3 sensitivity enhancement for the spray numbers ranging from two to nine compared to a conventional single Electrospray ionization source under the same operating conditions.

  • microfabricated isoelectric focusing device for direct Electrospray ionization mass spectrometry
    Electrophoresis, 2000
    Co-Authors: Jenny Wen, Harold R. Udseth, Yuehe Lin, Dean W Matson, Fan Xiang, Richard D. Smith
    Abstract:

    A novel microfabricated device for isoelectric focusing (IEF) incorporating an optimized Electrospray ionization (ESI) tip was constructed on polycarbonate plates using laser micromachining. The IEF microchip incorporated a separation channel (50 μ × 30 μ × 16 cm), three fluid connectors, and two buffer reservoirs. Electrical potentials used for IEF focusing and Electrospray were applied through platinum electrodes placed in the buffer reservoirs, which were isolated from the separation channel by porous membranes. Direct ESI-mass spectrometry (MS) using Electrosprays produced directly from a sharp emitter „tip” on the microchip was evaluated. The results indicated that this design can produce a stable Electrospray and that performance was further improved and made more flexible with the assistance of a sheath gas and sheath liquid. Error analysis of the spectral data showed that the standard deviation in signal intensity for an analyte peak was less than ˜ 5% over 3 h. The production of stable Electrosprays directly from microchip IEF device represents a step towards easily fabricated microanalytical devices. Microchannel IEF separations of protein mixtures were demonstrated for uncoated polycarbonate microchips. Direct microchannel IEF-ESI-MS was demonstrated using the microfabricated chip with an ion-trap mass spectrometer for characterization of protein mixtures.

Richard D Oleschuk - One of the best experts on this subject based on the ideXlab platform.

  • polymer micronozzle array for multiple Electrosprays produced by templated synthesis and etching of microstructured fibers
    Analytical Chemistry, 2015
    Co-Authors: Yueqiao Fu, Graham T T Gibson, Antoine Proulx, Andre Croteau, Bradley B Schneider, Thomas R Covey, Richard D Oleschuk
    Abstract:

    Microstructured fibers (MSFs) having raised polymer nozzles in each channel are custom designed, fabricated, and tested for use as multiple Electrospray (MES) emitters for mass spectrometry (MS). There is strong motivation to develop Electrospray emitters that operate at practical flow rates but give the much greater ionization efficiency associated with lower (nano) flow rates. This can be accomplished by splitting the flow into many lower-volume Electrosprays, an approach known as MES. To couple with most modern mass spectrometers, the MES emitter must have a small diameter to allow efficient ion collection into the MS. In this work, a MSF, defined as a fiber having many empty channels running along its length, was designed to have 9 channels, 9 μm each, >100 μm apart arranged in a radial pattern, all in a fiber having a compatible diameter with both front-end LC equipment and typical MS inlets. This design seeks to promote independent Electrospray from each channel while maintaining electric field homo...

  • Polymer Micronozzle Array for Multiple Electrosprays Produced by Templated Synthesis and Etching of Microstructured Fibers
    2015
    Co-Authors: Graham T T Gibson, Antoine Proulx, Andre Croteau, Thomas R Covey, Bradley B. Schneider, Richard D Oleschuk
    Abstract:

    Microstructured fibers (MSFs) having raised polymer nozzles in each channel are custom designed, fabricated, and tested for use as multiple Electrospray (MES) emitters for mass spectrometry (MS). There is strong motivation to develop Electrospray emitters that operate at practical flow rates but give the much greater ionization efficiency associated with lower (nano) flow rates. This can be accomplished by splitting the flow into many lower-volume Electrosprays, an approach known as MES. To couple with most modern mass spectrometers, the MES emitter must have a small diameter to allow efficient ion collection into the MS. In this work, a MSF, defined as a fiber having many empty channels running along its length, was designed to have 9 channels, 9 μm each, >100 μm apart arranged in a radial pattern, all in a fiber having a compatible diameter with both front-end LC equipment and typical MS inlets. This design seeks to promote independent Electrospray from each channel while maintaining electric field homogeneity. While the MSFs themselves do not support MES, the formation of polymer nozzles protruding from each channel at the tip face enables independent Electrospray from each nozzle. Microscope imaging, Electrospray current measurement, and ESI-MS detection of a model analyte all confirm the MES behavior of the 9-nozzle emitter, showing significant signal enhancement relative to a single-nozzle emitter at the same total flow rate. LC/MS data from a protein digest obtained at an independent laboratory demonstrates the applicability and robustness of the emitter for real scientific challenges using modern LC/MS equipment

  • multiple Electrosprays generated from a single polycarbonate microstructured fibre
    Journal of Mass Spectrometry, 2012
    Co-Authors: Graham T T Gibson, Ramin D Wright, Richard D Oleschuk
    Abstract:

    Electrospray ionization (ESI) has been invaluable to the mass spectrometric detection of biomolecules, due largely to the sensitivity afforded by the ionization technique. Lower flow rates, e.g. in the nanoElectrospray regime, result in smaller initial Electrosprayed droplets, leading to higher ionization efficiency and greater signal. One approach to improving sensitivity without lowering flow rate is to generate multiple Electrosprays (MESs) from the same sample, essentially splitting one larger flow into smaller flows in the nanoESI regime. Presented here is a series of novel MES emitters in the form of polycarbonate fibres. Based on microstructured fibre (MSF) technology whereby a set of homogeneous parallel channels are formed in a heat-drawn fibre intended to conduct light, a custom design was fabricated in which 3, 6, 9 and 12 holes were arranged in a radial pattern to prevent inhomogeneities in the electric field. The MSFs have dimensions that are compatible with current standards in nanoESI equipment, and the tip is more compatible with standard MS orifices than other larger multiElectrospray emitters. By measuring the spray current provided by the various emitters under the same solvent/voltage/total flow rate conditions, a plot was obtained clearly demonstrating the expected dependence on the square root of the number of holes, i.e. the number of independent Electrosprays. With this firm proof of principle using this design/format, further effort is justified in developing similar emitters in alternative materials that better prevent surface wetting and allow greater hole density, ultimately leading to greater signal enhancement.