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High Voltage (high + voltage)
Selected AbstractsThe Origin of the High Voltage in DPM12/P3HT Organic Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 16 2010Antonio Sánchez-Díaz Abstract Organic solar cells made using a blend of DPM12 and P3HT are studied. The results show that higher Voc can be obtained when using DPM12 in comparison to the usual mono-substituted PCBM electron acceptor. Moreover, better device performances are also registered when the cells are irradiated with sun-simulated light of 10,50 mW cm,2 intensity. Electrochemical and time-resolved spectroscopic measurements are compared for both devices and a 100-mV shift in the density of states (DOS) is observed for DPM12/P3HT devices with respect to PCBM/P3HT solar cells and slow polaron-recombination dynamics are found for the DPM12/P3HT devices. These observations can be directly correlated with the observed increase in Voc, which is in contrast with previous results that correlated the higher Voc with different ideality factors obtained using dark-diode measurements. The origin for the shift in the DOS can be correlated to the crystallinity of the blend that is influenced by the properties of the included fullerene. [source] Effect of Operating Parameters on the Condensation of Ammonium Sulfate by ElectrodialysisCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 9 2008H. Yang Abstract The separation of ammonium sulfate from dilute solution by electrodialysis was investigated. From the results obtained, it is suggested that it is feasible to separate ammonium sulfate from aqueous solution by electrodialysis. The removal performance of ammonium sulfate obtained was very satisfactory. The optimal cation and anion membranes were found. The removal efficiencies were influenced by voltage, initial concentration, flow rate and temperature. High voltage and high temperature are beneficial to this separation process, but high fluid flow rate and concentrated initial concentration prolong the operation time required to achieve the target value. It was found that the optimal outlet concentration is 1,g/L, since the operation time is prolonged almost two-fold if the outlet concentration is decreased from 1,g/L to 0.5,g/L. [source] T-type calcium channels: an emerging therapeutic target for the treatment of painDRUG DEVELOPMENT RESEARCH, Issue 4 2006Terrance P. Snutch Abstract It has become generally accepted that presynaptic high voltage,activated N-type calcium channels located in the spinal dorsal horn are a validated clinical target for therapeutic interventions associated with severe intractable pain. Low voltage,activated (T-type) calcium channels play a number of critical roles in nervous system function, including controlling thalamocortical bursting behaviours and the generation of spike wave discharges associated with slow wave sleep patterns. There is a growing body of evidence that T-type calcium channels also contribute in several ways to both acute and neuropathic nociceptive behaviours. In the one instance, the Cav3.1 T-type channel isoform likely contributes an anti-nociceptive function in thalamocortical central signalling, possibly through the activation of inhibitory nRT neurons. In another instance, the Cav3.2 T-type calcium channel subtype acts at the level of primary afferents in a strongly pro-nociceptive manner in both acute and neuropathic models. While a number of classes of existing clinical agents non-selectively block T-type calcium channels, there are no subtype-specific drugs yet available. The development of agents selectively targeting peripheral Cav3.2 T-type calcium channels may represent an attractive new avenue for therapeutic intervention. Drug Dev. Res. 67:404,415, 2006. © 2006 Wiley-Liss, Inc. [source] Fine surface processing of LiNbO3 single crystals by maskless etching using NF3 system gas plasma RIEELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 2 2010Teruaki Omata Abstract The possibility of deep etching by plasma reactive ion etching (RIE) without an etching-mask (maskless) for ,Z and +Z parts formed on the same surface of a partially polarization reversed LiNbO3 single crystal polarized in the direction of the c -axis is investigated. A NF3/H2 gas mixture was used. The etching rates and depths and the profiles of the etched surfaces were evaluated by atomic force microscopy (AFM) and optical microscopy. The etching rate for the ,Z surface was larger than that for the +Z surface. Extension of the +Z domain by partial polarization reversal was observed. Applying the high voltage quickly for partial polarization reversal, the area of the +Z domain was extended compared with the result obtained by applying the voltage slowly. An apparent step at the boundary between ,Z and +Z parts formed on the same surface was observed. Using a NF3/H2 gas mixture, the segments were removed efficiently. It is concluded that RIE etching using a NF3/H2 gas mixture is suitable for processing of LiNbO3 crystal surfaces without an etching mask, in contrast with a CF4/H2 gas mixture. © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(2): 39,49, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10168 [source] On-column conductivity detection in capillary-chip electrophoresisELECTROPHORESIS, Issue 24 2007Zhi-Yong Wu Professor Abstract On-column conductivity detection in capillary-chip electrophoresis was achieved by actively coupling the high electric field with two sensing electrodes connected to the main capillary channel through two side detection channels. The principle of this concept was demonstrated by using a glass chip with a separation channel incorporating two double-Ts. One double-T was used for sample introduction, and the other for detection. The two electrophoresis electrodes apply the high voltage and provide the current, and the two sensing electrodes connected to the separation channel through the second double-T and probe a potential difference. This potential difference is directly related to the local resistance or the conductivity of the solution defined by the two side channels on the main separation channel. A detection limit of 15,,M (600,ppb or 900,fg) was achieved for potassium ion in a 2,mM Tris-HCl buffer (pH,8.7) with a linear range of 2 orders of magnitude without any stacking. The proposed detection method avoids integrating the sensing electrodes directly within the separation channel and prevents any direct contact of the electrodes with the sample. The baseline signal can also be used for online monitoring of the electric field strength and electroosmosis mobility characterization in the separation channel. [source] High-efficiency peptide analysis on monolithic multimode capillary columns: Pressure-assisted capillary electrochromatography/capillary electrophoresis coupled to UV and electrospray ionization-mass spectrometryELECTROPHORESIS, Issue 21 2003Alexander R. Ivanov Abstract High-efficiency peptide analysis using multimode pressure-assisted capillary electrochromatography/capillary electrophoresis (pCEC/pCE) monolithic polymeric columns and the separation of model peptide mixtures and protein digests by isocratic and gradient elution under an applied electric field with UV and electrospray ionization-mass spectrometry (ESI-MS) detection is demonstrated. Capillary multipurpose columns were prepared in silanized fused-silica capillaries of 50, 75, and 100 ,m inner diameters by thermally induced in situ copolymerization of methacrylic monomers in the presence of n -propanol and formamide as porogens and azobisisobutyronitrile as initiator. N -Ethylbutylamine was used to modify the chromatographic surface of the monolith from neutral to cationic. Monolithic columns were termed as multipurpose or multimode columns because they showed mixed modes of separation mechanisms under different conditions. Anion-exchange separation ability in the liquid chromatography (LC) mode can be determined by the cationic chromatographic surface of the monolith. At acidic pH and high voltage across the column, the monolithic stationary phase provided conditions for predominantly capillary electrophoretic migration of peptides. At basic pH and electric field across the column, enhanced chromatographic retention of peptides on monolithic capillary column made CEC mechanisms of migration responsible for separation. The role of pressure, ionic strength, pH, and organic content of the mobile phase on chromatographic performance was investigated. High efficiencies (exceeding 300,000 plates/m) of the monolithic columns for peptide separations are shown using volatile and nonvolatile, acidic and basic buffers. Good reproducibility and robustness of isocratic and gradient elution pressure-assisted CEC/CE separations were achieved for both UV and ESI-MS detection. Manipulation of the electric field and gradient conditions allowed high-throughput analysis of complex peptide mixtures. A simple design of sheathless electrospray emitter provided effective and robust low dead volume interfacing of monolithic multimode columns with ESI-MS. Gradient elution pressure-assisted mixed-mode separation CE/CEC-ESI-MS mass fingerprinting and data-dependent pCE/pCEC-ESI-MS/MS analysis of a bovine serum albumin (BSA) tryptic digest in less than 5 min yielding high sequence coverage (73%) demonstrated the potential of the method. [source] 5-HT inhibits N-type but not L-type Ca2+ channels via 5-HT1A receptors in lamprey spinal neuronsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2003Russell H. Hill Abstract 5-HT is a potent modulator of locomotor activity in vertebrates. In the lamprey, 5-HT dramatically slows fictive swimming. At the neuronal level it reduces the postspike slow afterhyperpolarization (sAHP), which is due to apamin-sensitive Ca2+ -dependent K+ channels (KCa). Indirect evidence in early experiments suggested that the sAHP reduction results from a direct action of 5-HT on KCa channels rather than an effect on the Ca2+ entry during the action potential [Wallén et al., (1989) J. Neurophysiol., 61, 759,768]. In view of the characterization of different subtypes of Ca2+ channels with very different properties, we now reinvestigate if there is a selective action of 5-HT on a Ca2+ channel subtype in dissociated spinal neurons in culture. 5-HT reduced Ca2+ currents from high voltage activated channels. N-type, but not L-type, Ca2+ channel blockers abolished this 5-HT-induced reduction. It was also confirmed that 5-HT depresses Ca2+ currents in neurons, including motoneurons, in the intact spinal cord. 8-OH-DPAT, a 5-HT1A receptor agonist, also inhibited Ca2+ currents in dissociated neurons. After incubation in pertussis toxin, to block Gi/o proteins, 5-HT did not reduce Ca2+ currents, further indicating that the effect is caused by an activation of 5-HT1A receptors. As N-type, but not L-type, Ca2+ channels are known to mediate the activation of KCa channels and presynaptic transmitter release at lamprey synapses, the effects of 5-HT reported here can contribute to a reduction in both actions. [source] Voltage-gated ionic currents in an identified modulatory cell type controlling molluscan feedingEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2002Kevin Staras Abstract An important modulatory cell type, found in all molluscan feeding networks, was investigated using two-electrode voltage- and current-clamp methods. In the cerebral giant cells of Lymnaea, a transient inward Na+ current was identified with activation at ,58 ± 2 mV. It was sensitive to tetrodotoxin only in high concentrations (, 50% block at 100 µm), a characteristic of Na+ channels in many molluscan neurons. A much smaller low-threshold persistent Na+ current (activation at <,,90 mV) was also identified. Two purely voltage-sensitive outward K+ currents were also found: (i) a transient A-current type which was activated at ,59 ± 4 mV and blocked by 4-aminopyridine; (ii) a sustained tetraethylammonium-sensitive delayed rectifier current which was activated at ,47 ± 2 mV. There was also evidence that a third, Ca2+ -activated, K+ channel made a contribution to the total outward current. No inwardly rectifying currents were found. Two Ca2+ currents were characterized: (i) a transient low-voltage (,65 ± 2 mV) activated T-type current, which was blocked in NiCl2 (2 mm) and was completely inactivated at ,,,50 mV; (ii) A sustained high voltage (,40 ± 1 mV) activated current, which was blocked in CdCl2 (100 µm) but not in ,-conotoxin GVIA (10 µm), ,-agatoxin IVA (500 nm) or nifedipine (10 µm). This current was enhanced in Ba2+ saline. Current-clamp experiments revealed how these different current types could define the membrane potential and firing properties of the cerebral giant cells, which are important in shaping the wide-acting modulatory influence of this neuron on the rest of the feeding network. [source] Two-dimensional finite element thermal modeling of an oil-immersed transformerEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 6 2008Jawad Faiz Abstract Finite element (FE) modeling of a typical transformer indicates that the hot spot position is always on the top most part of the transformer. The hot spot temperature of winding depends on the load and the type of loading and is changed by loading. A number of the generated magnetic flux lines of windings close to their paths perpendicular to the internal channel of the windings and therefore the flux density in the middle of the channel is considerably larger than the beginning and ending of the winding. Two models of windings are employed and different temperature distributions are obtained. The computation results show that the time constant of high voltage (HV) winding is lower than that of the low voltage (LV) winding. A good agreement between the test and computed results has been achieved. Copyright © 2007 John Wiley & Sons, Ltd. [source] Ultrathin, Organic, Semiconductor/Polymer Blends by Scanning Corona-Discharge Coating for High-Performance Organic Thin-Film TransistorsADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Hee Joon Jung Abstract A new thin-film coating process, scanning corona-discharge coating (SCDC), to fabricate ultrathin tri-isopropylsilylethynyl pentacene (TIPS-PEN)/amorphous-polymer blend layers suitable for high-performance, bottom-gate, organic thin-film transistors (OTFTs) is described. The method is based on utilizing the electrodynamic flow of gas molecules that are corona-discharged at a sharp metallic tip under a high voltage and subsequently directed towards a bottom electrode. With the static movement of the bottom electrode, on which a blend solution of TIPS-PEN and an amorphous polymer is deposited, SCDC provides an efficient route to produce uniform blend films with thicknesses of less than one hundred nanometers, in which the TIPS-PEN and the amorphous polymer are vertically phase-separated into a bilayered structure with a single-crystalline nature of the TIPS-PEN. A bottom-gate field-effect transistor with a blend layer of TIPS-PEN/polystyrene (PS) (90/10 wt%) operated at ambient conditions, for example, indeed exhibits a highly reliable device performance with a field-effect mobility of approximately 0.23 cm2 V,1 s,1: two orders of magnitude greater than that of a spin-coated blend film. SCDC also turns out to be applicable to other amorphous polymers, such as poly(, -methyl styrene) and poly(methyl methacrylate) and, readily combined with the conventional transfer-printing technique, gives rise to micropatterned arrays of TIPS-PEN/polymer films. [source] Hybrid Nanoparticle/Organic Devices with Strong Resonant Tunneling BehaviorsADVANCED FUNCTIONAL MATERIALS, Issue 16 2009Tianhang Zheng Abstract A hybrid nanoparticle/organic device consisting of small molecule organic semiconductors and Ag nanoparticles is reported. The single device exhibits unusual properties of organic resonant tunneling diode (ORTD) at low driving voltage region and offers light emission at high voltage. For ORTD, a strong negative differential resistance behavior is demonstrated at room temperature. The current resonance with the peak-to-valley current ratio of over 4.6 and narrow linewidth of only ,1.4,V is achieved. A detailed operating mechanism of the charging and emission modes is proposed, which can be discussed in terms of the strong charge-trapping effect of Ag nanoparticles. The repeatable operations of hybrid device show the mutual influences between two modes and the light emission properties of the ORTD are also discussed. [source] Forensic Characteristics of Suicide by Electrocution in BulgariaJOURNAL OF FORENSIC SCIENCES, Issue 3 2009William Dokov M.D. Abstract:, Suicides by electrocution (SE) are relatively rare and insufficiently studied. The purpose of this study is to present a more detailed picture of SE in Bulgaria. Forensic medical files of 59 SE cases were examined. spss 11.0 software was applied to produce the descriptive statistical analyses. Values of p < 0.05 were assumed to be statistically significant. We studied 59 SE cases, which account for 6.24% of all deaths by electrocution and 0.09% of all forensic autopsies. The average age of victims was 45.19 years old. Males prevailed: 91.53%. Children below 18 years old accounted for 3.39%. 42.37% of the victims applied low voltage (<220 V), and 33.99% applied high voltage (>220 V). The preferred method of SE was by direct contact victim/electrical cable: 47.45%. The summer months June through September account for 49.15% of all cases. [source] Pressure-Assisted Spinning: A Versatile and Economical, Direct Fibre to Scaffold Spinning MethodologyMACROMOLECULAR RAPID COMMUNICATIONS, Issue 14 2007Sumathy Arumuganathar Abstract Spinning composite polymer fibres by means of electric fields has been investigated for well over a century. These spun fibres have been explored across many areas of research, spanning the physical to the life sciences; however, electrospinning has the hazardous nature of the high voltage at the spinning needle. We demonstrate here a competing direct fibre to scaffold preparation method, completely determined by an applied pressure. Our technique reported here removes the hazardous high-voltage element from the fibre/scaffold formation technique and has the ability to form uniaxial fibres and scaffolds comparable to those fabricated by electrospinning. We refer to this fibre generation approach as "pressure-assisted spinning (PAS)", which will have a tremendous impact in a range of applications, spanning the physical through to the life sciences. PAS joins the techniques for fibre to scaffold generation with a view to significantly and globally contributing to the micro- and nanosciences. [source] Analysis of leakage currents in photovoltaic modules under high-voltage bias in the field,PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 1 2002J. A. del Cueto As photovoltaic modules become more widely disseminated in high-power or utility-power applications, their ability to withstand high voltage relative to ground becomes a reliability issue. Long-term effects of exposure to high-voltage stress in the field are investigated. Starting in early 1998, four commercially available PV modules inaugurated the high-voltage stress test at the Outdoor Test Facility at NREL. Modules representing both crystalline and amorphous silicon technologies were deployed on the high-voltage stress testbed located outdoors in order to simulate and assess operation in high-voltage array configurations. They were biased at positive and negative polarity 600 V at all times,except for 1 min at noon each day, when they were subjected to 2200 V bias,and their leakage currents to ground were monitored continuously. The ubiquitous effects of moisture on leakage conductance are analyzed. Module leakage conductance is found to be thermally activated with a characteristic energy that depends on relative humidity. Separate current paths likely responsible for leakage conductance are analyzed and identified at opposite ends of the relative humidity range. Leakage current data are integrated against time to arrive at accumulated charge due to long-term, high-voltage exposure. Published in 2002 by John Wiley & Sons, Ltd. [source] Accurate mass measurement in nano-electrospray ionization mass spectrometry by alternate switching of high voltage between sample and reference sprayersRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 4 2005Yoshinori Satomi An electrospray dual sprayer, which generates separate sample and reference sprays by alternately switching the high voltage between the two sprayers, is described. The technique permits accurate mass measurements in nano-electrospray ionization mass spectrometry (ESI-MS) to be obtained using a quadrupole/orthogonal acceleration time-of-flight mass spectrometer (Q-TOF). Similar to the method employed with a dual ESI source (Wolff JC et al., Anal. Chem. 2001; 73: 2605), the two sprays are orthogonal with respect to each other, but can be independently sampled without any baffle between these sprays. The reference sprayer is used in the original configuration of the ESI source and was optimized for a 1,2,,L/min flow, whereas the sample sprayer can be either a conventional glass capillary or a borosilicate tip of the type used for nano-ESI. Both sprayers can be positioned close to the cone so as to give maximum ion currents. The sample and reference sprays are independently generated by raising the potentials on the sample and reference sprayers to 1.4 and 3.0,kV, respectively; the high voltages can be rapidly turned on and off in ca. 1,ms. A nano-ESI-MS or nano-flow LC/ESI-MS experiment using a Q-TOF coupled with the above system gave mass accuracies within 3,ppm for measurements of ions up to m/z 1000 using subpicomole samples. Copyright © 2005 John Wiley & Sons, Ltd. [source] Continuous-flow sample introduction for field desorption/ionization mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2004Tanner M. Schaub We introduce continuous-flow field desorption (FD) for improved spectral quality, higher sample throughput, and simpler interface to sample handlers and chromatographic equipment. A recently developed commercial FD probe with integral fused-silica capillary allows sample dosing in situ, without probe removal and reinsertion. A stable FD-generated ion current can be sustained for longer than an hour by continuous deposition of analyte solution on the FD emitter heated and at high voltage. Continuous-flow FD allows ensemble averaging of up to 100 Fourier transform ion cyclotron resonance (FT-ICR) mass spectra, in contrast to the traditional emitter dosing technique. Continuous-flow FD is amenable to interface with liquid chromatography (LC) and/or automated sample injectors. Copyright © 2004 John Wiley & Sons, Ltd. [source] Exposure assessment of electromagnetic fields near electrosurgical unitsBIOELECTROMAGNETICS, Issue 7 2010Jonna Wilén Abstract Electrosurgical units (ESU) are widely used in medical health services. By applying sinusoidal or pulsed voltage in the frequency range of 0.3,5,MHz to the electrode tip, the desired mixture of coagulation and cutting are achieved. Due to the high voltage and current in the cable, strong electromagnetic fields appear near the ESU. The surgeon and others inside the operating room such as nurses, anesthesiologists, etc., will be highly exposed to these fields. The stray fields surrounding the ESU have previously been measured, but now a deeper analysis has been made of the curve shape of the field and the implication of this when assessing exposure from a commonly used ESU in accordance with the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines. The result showed that for some of the modes, especially those using high-pulsed voltage with only a few sinusoidal periods, the E-field close to the cable could reach linear spatially averaged values of 20,kV/m compared to the 2.1,kV/m stated in ICNIRP guidelines. Assessing the E- and B-field from ESU is not straightforward since in this frequency range, both induced current density and specific absorption rate are restricted by the ICNIRP guidelines. Nevertheless, work needs to be done to reduce the stray fields from ESU. Bioelectromagnetics 31:513,518, 2010. © 2010 Wiley-Liss, Inc. [source] Investigating DNA migration in pulsed fields using a miniaturized FIGE systemELECTROPHORESIS, Issue 23 2008Xiaojia Chen Abstract PFGE is a well-established technique for fractionation of DNA fragments ranging from kilobases to megabases in length. But many of these separations require an undesirable combination of long experiment times (often approaching tens of hours) and application of high voltages (often approaching tens of kV). Here, we present a simple miniaturized FIGE apparatus capable of separating DNA fragments up to 32.5,kb in length within 3,h using a modest applied potential of 20,V. The device is small enough to be imaged under a fluorescence microscope, permitting the migrating DNA bands to be observed during the course of the separation run. We use this capability to investigate how separation performance is affected by parameters including the ratio of forward and backward voltage, pulse time, and temperature. We also characterize the dependence of DNA mobility on fragment size N, and observe a scaling in the vicinity of N,0.5 over the size range investigated. The high speed, low power consumption, and simple design of this system may help enable future studies of DNA migration in PFGE to be performed quickly and inexpensively. [source] Conductance through a redox system in the Coulomb blockade regime: Many-particle effects and influence of electronic correlationsPHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 1-2 2010Sabine Tornow Abstract We investigate the transport characteristics of a redox system weakly coupled to leads in the Coulomb blockade regime. The redox system comprises a donor and acceptor separated by an insulating bridge in a solution. It is modeled by a two-site extended Hubbard model which includes on-site and inter-site Coulomb interactions and the coupling to a bosonic bath. The current,voltage characteristics is calculated at high temperatures using a rate equation approach. For high voltages exceeding the Coulomb repulsion at the donor site the calculated transport characteristics exhibit pronounced deviations from the behavior expected from single-electron transport. Depending on the relative sizes of the effective on-site and inter-site Coulomb interactions on one side and the reorganization energy on the other side we find either negative differential resistance or current enhancement. Schematic view of the redox system with donor (D) and acceptor (A) coupled to the leads L and R. The electronic degrees of freedom of the DA system are coupled to the environment comprising internal vibrations and the solvent dynamics. The current is calculated as a function of the bias voltage Vb and gate voltage Vg. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Corrosion effects in thin-film photovoltaic modulesPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 6 2003D. E. Carlson Abstract Electrochemical corrosion effects can occur in thin-film photovoltaic (PV) modules that are fabricated on tin-oxide-coated glass when operating at high voltages and at elevated temperatures in a humid climate. The current study shows that this corrosion is associated with a delamination of the tin oxide layer from the glass, which is caused by sodium accumulation near the interface between the tin oxide and the glass and by the ingression of moisture into the PV module from the edges. This corrosion in thin-film PV modules can be significantly reduced by altering the growth conditions of the tin oxide or by using zinc oxide as a transparent conductive oxide electrode. Copyright © 2003 John Wiley & Sons, Ltd. [source] Desorption sonic spray ionization for (high) voltage-free ambient mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 19 2006Renato Haddad Sonic spray ionization is shown to create a supersonic cloud of charged droplets able to promote efficient desorption and ionization of drugs directly from the surfaces of commercial drug tablets at ambient conditions. Compared with desorption electrospray ionization (DESI), desorption sonic spray ionization (DeSSI) is advantageous since it uses neither heating nor high voltages at the spray capillary. DeSSI therefore provides a more friendly environment in which to perform ambient mass spectrometry (MS). DeSSI-MS is herein evaluated for the analysis of drug tablets, and found to be, in general, as sensitive as DESI-MS. The (high) voltage-free DeSSI method provides, however, cleaner mass spectra with less abundant solvent cluster ions and with enough abundant analyte signal for tandem mass spectrometry (MS/MS). These features may therefore facilitate the DeSSI-MS detection of low molar mass components or impurities, or both. The higher-velocity supersonic DeSSI spray also facilitates matrix penetration thus providing more homogenous sampling and longer lasting ion signals. Copyright © 2006 John Wiley & Sons, Ltd. [source] Accurate mass measurement in nano-electrospray ionization mass spectrometry by alternate switching of high voltage between sample and reference sprayersRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 4 2005Yoshinori Satomi An electrospray dual sprayer, which generates separate sample and reference sprays by alternately switching the high voltage between the two sprayers, is described. The technique permits accurate mass measurements in nano-electrospray ionization mass spectrometry (ESI-MS) to be obtained using a quadrupole/orthogonal acceleration time-of-flight mass spectrometer (Q-TOF). Similar to the method employed with a dual ESI source (Wolff JC et al., Anal. Chem. 2001; 73: 2605), the two sprays are orthogonal with respect to each other, but can be independently sampled without any baffle between these sprays. The reference sprayer is used in the original configuration of the ESI source and was optimized for a 1,2,,L/min flow, whereas the sample sprayer can be either a conventional glass capillary or a borosilicate tip of the type used for nano-ESI. Both sprayers can be positioned close to the cone so as to give maximum ion currents. The sample and reference sprays are independently generated by raising the potentials on the sample and reference sprayers to 1.4 and 3.0,kV, respectively; the high voltages can be rapidly turned on and off in ca. 1,ms. A nano-ESI-MS or nano-flow LC/ESI-MS experiment using a Q-TOF coupled with the above system gave mass accuracies within 3,ppm for measurements of ions up to m/z 1000 using subpicomole samples. Copyright © 2005 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||