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ESI Source (esi + source)
Selected AbstractsThe Orbitrap: a new mass spectrometerJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 4 2005Qizhi Hu Abstract Research areas such as proteomics and metabolomics are driving the demand for mass spectrometers that have high performance but modest power requirements, size, and cost. This paper describes such an instrument, the Orbitrap, based on a new type of mass analyzer invented by Makarov. The Orbitrap operates by radially trapping ions about a central spindle electrode. An outer barrel-like electrode is coaxial with the inner spindlelike electrode and mass/charge values are measured from the frequency of harmonic ion oscillations, along the axis of the electric field, undergone by the orbitally trapped ions. This axial frequency is independent of the energy and spatial spread of the ions. Ion frequencies are measured non-destructively by acquisition of time-domain image current transients, with subsequent fast Fourier transforms (FFTs) being used to obtain the mass spectra. In addition to describing the Orbitrap mass analyzer, this paper also describes a complete Orbitrap-based mass spectrometer, equipped with an electrospray ionization source (ESI). Ions are transferred from the ESI source through three stages of differential pumping using RF guide quadrupoles. The third quadrupole, pressurized to less than 10,3 Torr with collision gas, acts as an ion accumulator; ion/neutral collisions slow the ions and cause them to pool in an axial potential well at the end of the quadrupole. Ion bunches are injected from this pool into the Orbitrap analyzer for mass analysis. The ion injection process is described in a simplified way, including a description of electrodynamic squeezing, field compensation for the effects of the ion injection slit, and criteria for orbital stability. Features of the Orbitrap at its present stage of development include high mass resolution (up to 150 000), large space charge capacity, high mass accuracy (2,5 ppm), a mass/charge range of at least 6000, and dynamic range greater than 10.3 Applications based on electrospray ionization are described, including characterization of transition-metal complexes, oligosaccharides, peptides, and proteins. Use is also made of the high-resolution capabilities of the Orbitrap to confirm the presence of metaclusters of serine octamers in ESI mass spectra and to perform H/D exchange experiments on these ions in the storage quadrupole. Copyright © 2005 John Wiley & Sons, Ltd. [source] Electrospray mass spectrometry of stable iminyl nitroxide and nitronyl nitroxide free radicalsJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 9 2002Craig D. Smith Abstract Electrospray ionization (ESI) mass spectra have been recorded for a range of substituted nitronyl nitroxide and iminyl nitroxide monoradicals and biradicals. Secondary species formed in the ESI source were observed as the dominant ions in both the iminyl nitroxide and nitronyl nitroxide spectra. Daughter ion spectrometry was used to establish fragmentation mechanisms for the nitronyl nitroxide and iminyl nitroxide moieties as well as the secondary species under ESI conditions. Copyright © 2002 John Wiley & Sons, Ltd. [source] Gas-phase binding of non-covalent protein complexes between bovine pancreatic trypsin inhibitor and its target enzymes studied by electrospray ionization tandem mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 8 2001Victor J. Nesatyy Abstract The potential of electrospray ionization (ESI) mass spectrometry (MS) to detect non-covalent protein complexes has been demonstrated repeteadly. However, questions about correlation of the solution and gas-phase structures of these complexes still produce vigorous scientific discussion. Here, we demonstrate the evaluation of the gas-phase binding of non-covalent protein complexes formed between bovine pancreatic trypsin inhibitor (BPTI) and its target enzymes over a wide range of dissociation constants. Non-covalent protein complexes were detected by ESI-MS. The abundance of the complex ions in the mass spectra is less than expected from the values of the dissociation constants of the complexes in solution. Collisionally activated dissociation (CAD) tandem mass spectrometry (MS/MS) and a collision model for ion activation were used to evaluate the binding of non-covalent complexes in the gas phase. The internal energy required to induce dissociation was calculated for three collision gases (Ne, Ar, Kr) over a wide range of collision gas pressures and energies using an electrospray ionization source. The order of binding energies of the gas-phase ions for non-covalent protein complexes formed by the ESI source and assessed using CAD-MS/MS appears to differ from that of the solution complexes. The implication is that solution structure of these complexes was not preserved in the gas phase. Copyright © 2001 John Wiley & Sons, Ltd. [source] Desorption electrospray ionization mass spectrometric analysis of organophosphorus chemical warfare agents using ion mobility and tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 11 2010Paul A. D'Agostino Desorption electrospray ionization mass spectrometry (DESI-MS) has been applied to the direct analysis of sample media for target chemicals, including chemical warfare agents (CWA), without the need for additional sample handling. During the present study, solid-phase microextraction (SPME) fibers were used to sample the headspace above five organophosphorus CWA, O -isopropyl methylphosphonofluoridate (sarin, GB), O -pinacolyl methylphosphonofluoridate (soman, GD), O -ethyl N,N -dimethyl phosphoramidocyanidate (tabun, GA), O -cyclohexyl methylphosphonofluoridate (cyclohexyl sarin, GF) and O -ethyl S-2-diisopropylaminoethyl methyl phosphonothiolate (VX) spiked into glass headspace sampling vials. Following sampling, the SPME fibers were introduced directly into a modified ESI source, enabling rapid and safe DESI of the toxic compounds. A SYNAPT HDMSŌ instrument was used to acquire time-aligned parallel (TAP) fragmentation data, which provided both ion mobility and MSn (n,=,2 or 3) data useful for the confirmation of CWA. Unique ion mobility profiles were acquired for each compound and characteristic product ions of the ion mobility separated ions were produced in the TriwaveŌ transfer collision region. Up to six full scanning MSn spectra, containing the [M,+,H]+ ion and up to seven diagnostic product ions, were acquired for each CWA during SPME fiber analysis. A rapid screening approach, based on the developed methodology, was applied to several typical forensic media, including Dacron sampling swabs spiked with 5,µg of CWA. Background interference was minimal and the spiked CWA were readily identified within one minute on the basis of the acquired ion mobility and mass spectrometric data. Copyright © 2010 Crown in the right of Canada. Published by John Wiley & Sons, Ltd. [source] Molecular mass ranges of coal tar pitch fractions by mass spectrometry and size-exclusion chromatographyRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 13 2009F. Karaca A coal tar pitch was fractionated by solvent solubility into heptane-solubles, heptane-insoluble/toluene-solubles (asphaltenes), and toluene-insolubles (preasphaltenes). The aim of the work was to compare the mass ranges of the different fractions by several different techniques. Thermogravimetric analysis, size-exclusion chromatography (SEC) and UV-fluorescence spectroscopy showed distinct differences between the three fractions in terms of volatility, molecular size ranges and the aromatic chromophore sizes present. The mass spectrometric methods used were gas chromatography/mass spectrometry (GC/MS), pyrolysis/GC/MS, electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICRMS) and laser desorption time-of-flight mass spectrometry (LD-TOFMS). The first three techniques gave good mass spectra only for the heptane-soluble fraction. Only LDMS gave signals from the toluene-insolubles, indicating that the molecules were too involatile for GC and too complex to pyrolyze into small molecules during pyrolysis/GC/MS. ESI-FTICRMS gave no signal for toluene-insolubles probably because the fraction was insoluble in the methanol or acetonitrile, water and formic acid mixture used as solvent to the ESI source. LDMS was able to generate ions from each of the fractions. Fractionation of complex samples is necessary to separate smaller molecules to allow the use of higher laser fluences for the larger molecules and suppress the formation of ionized molecular clusters. The upper mass limit of the pitch was determined as between 5000 and 10,000,u. The pitch asphaltenes showed a peak of maximum intensity in the LDMS spectra at around m/z 400, in broad agreement with the estimate from SEC. The mass ranges of the toluene-insoluble fraction found by LDMS and SEC (400,10,000,u with maximum intensity around 2000,u by LDMS and 100,9320,u with maximum intensity around 740,u by SEC) are higher than those for the asphaltene fraction (200,4000,u with maximum intensity around 400,u by LDMS and 100,2680,u with maximum intensity around 286,u by SEC) and greater than values considered appropriate for petroleum asphaltenes (300,1200,u with maximum intensity near 700,u). Copyright © 2009 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] A combined ion source for fast switching between electrospray and matrix-assisted laser desorption/ionization in Fourier transform ion cyclotron resonance mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2002Gökhan Baykut A new ion source has been developed for Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) that enables quick changes between matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI) modes. When operating as an ESI source, the sample solution is sprayed through an angled nebulizer. The generated ions pass through a glass capillary followed by a skimmer and three sequential hexapole ion guides. Ions can be accumulated in the third hexapole (storage hexapole) before they are injected into the ICR trap. The second hexapole is mounted on a movable platform which also carries the MALDI sample plate. During the switch from ESI to MALDI, this platform moves the second hexapole out of the hexapole series and locates a MALDI sample plate with 384 sample positions into the area directly in front of the storage hexapole. The storage hexapole is in a medium pressure chamber (MPC) which has windows both for the incoming laser beam and for the observation optics, as well as a gas tube for pulsing collision gas into the chamber. During the MALDI operation the focused laser beam enters the MPC, passes between the hexapole rods and irradiates a MALDI sample on the target plate. The sample molecules are desorbed/ionized into the storage hexapole and simultaneously cooled by collisions with the pulsed gas. Ions desorbed from multiple laser shots can be accumulated in this hexapole before they are transferred to the ICR trap. With the combined ion source a computer-controlled switch between MALDI and ESI modes is possible in less than a minute, depending on the position of the MALDI target on the 384-spot plate. Immediate acquisition of mass spectra is possible after mode switching without the need for tuning or re-calibration. Copyright © 2002 John Wiley & Sons, Ltd. [source] Preliminary study of the analysis of oligogalacturonic acids by electrospray ionization mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 12 2001Liang Zhu During systematic studies of the behavior of oligogalacturonic acids (OGAs) under different conditions using electrospray ionization mass spectrometry (ESI-MS), cation adduction, fragmentation and non-covalent binding were found to be the three major problems that compromised the analysis of OGAs by ESI-MS. By adjusting solution components, capillary temperature and capillary voltage in the ESI source, an optimized condition was found that gave a clean and clear spectrum of trigalacturonic acid. A direct injection ESI-MS technique based on the use of aqueous acetonitrile and acetic acid and triethylamine (TEA) as modifiers has been applied to analyze a mixture including mono-, di- and trigalacturonic acids, which will facilitate further applications of ESI-MS in the analysis of mixtures of OGAs. Copyright © 2001 John Wiley & Sons, Ltd. [source] | ||||||||||