Ultrahigh-resolution-measurement

The best results are to be expected from stored waveform inverse Fourier transform (SWIFT) excitation [194]. First, the ideal excitation waveform is tailored to the needs of the intended experiment and then produced by an RF generator. SWIFT excitation also allows to remove ions of predefined m/z ranges from the ICR cell. This results in storage of a small m/z range, or after repeated SWIFT pulsing of a single nominal mass out of a broad band spectrum. Those ions are then accessible for ultrahigh resolution measurements or as precursors for tandem MS. 

Wu, Z. Rodgers, R. R Marshall, A. G. Two- and three-dimensional van Krevelen diagrams A graphical analysis complementary to the Kendrick mass plot for sorting elemental compositions of complex organic mixtures based on ultrahigh-resolution broadband Fourier transform ion cyclotron resonance mass measurements. Anal. Chem. 2004, 76, 2511-2516. 

Tohno et al. (20) used similar steps to determine the chromatin loop size in human leukemia cells (an ultrahigh-resolution EM was not needed). To determine chromatin loop size, the lengths of 102 chromatin fibers protruding from four nuclei were measured and their average lengths were estimated. The steps they used (essentially those of Miller and Bakken (21) are summarized as follows ... 

See also [89Morl] for the analysts of the FIRFT spectrum between 8 and 1(X) cm" and [89Mor2] for ultrahigh resolution FIR measurements. In these two analyses a Taylor series expansion in J J + 1) of the energy levels is used, see [84Her] for model used 8 = -66.57928 (7800)... 

ESI-FT-ICR mass spectrum of a GMA/BMA copolymer (a) 625 < m/z < 2100 (b) Ultrahigh resolution and accurate mass measurement for the GMA/BMA tetramer. (Reprinted with permission from Ref. 43. Copyright 1995 American Chemical Society.)... 

Mass spectrometry-based techniques to identify combinatorial libraries make use of ESI-MS [90], HPLC/ESI-MS [91], MALDI-MS [92], and a combination of ESI with IMS [93,94] and FT-ICR-MS [95,96]. The last one has the advantage that the molecular mass of the analyte can be measured at ultrahigh resolution to allow the separation of nominal isobaric ions. A better fingerprint of the library can be obtained at high mass resolution. 

Fig. 7.14 Ultrahigh-resolution of photoelectron spectra of Ba8Si46 measured at 5.4 K (superconducting state, open circles) and 10.0 K (normal state, open squares) using an energy resolution of 2.4 meV. Copyright American Institute of Physics [41]...

With the ultrahigh resolution, which can, in principle, be achieved with singlemode tunable lasers (Vol. 2, Chaps. 1-5), the accuracy of absolute wavelength measurements attainable with conventional techniques may not be satisfactory. New methods have been developed that are mainly based on interferometric measurements of laser wavelengths. For applications in molecular spectroscopy, the laser can be stabilized on the center of a molecular transition. Measuring the wavelength of such a stabihzed laser yields simultaneously the wavelength of the molecular... 

Wu, Z. Rodgers, R.P. Marshall, A.G. Two- and Three-Dimensianal Van Kiev-elen Diagrams A Grajdiical Analysis Complementary to the Kendrick Mass Plot for Sorting Elemental Compositions of Complex Organic Mixtures Based on Ultrahigh-Resolution Broadband Fourier Transform Ion Cyclotron Resonance Mass Measurements. Anal. Chem. 2004, 76,2511-2516. 

Watson, C. H. Barshick, C. M. Wronka, J. Laukien, F. H. Eyler, J. R. Pulsed gas glow discharge for ultrahigh mass resolution measurements with Fourier transform ion cyclotron resonance mass spectrometry. Anal. Chem. 1996, 68, 573-575. 

In theory, the SPOS technique can also be used to characterize the main, submicron portion of the PSD of polymer emulsions, rather than just their oversize tails. In practice, however, these ultrahigh-resolution techniques are confined to measuring the latter feature of the PSD, because of their limited detection threshold (sensitivity) - typically 0.5 jxm for commercially available SPOS sensors (LS method) of traditional design. However, the new high-concentration SPOS-LS technique is able to provide accurate quantitative information (no. of particles per milliliter) over most of the size range encompassed by the PSD - that is, down to 0.2 jxm, or even smaller. This qualitative improvement in sensitivity and working particle concentration (on the order of 10 particles per milliliter) allows SPOS to become one of the most important tools for characterizing the quality and stability of submicron polymer emulsions. 

Proper characterization of composite interfaces, whether it is for chemical, physical or mechanical properties, is extremely difficult because most interfaces with which we are concerned are buried inside the material. Furthermore, the microscopic and often nanoscopic nature of interfaces in most useful advanced fiber composites requires the characterization and measurement techniques to be of ultrahigh magnification and resolution for sensible and accurate solutions. In addition, experiments have to be carried out in a well-controlled environment using sophisticated testing conditions (e.g. in a high vacuum chamber). There are many difficulties often encountered in the physico-chemical analyses of surfaces. 

In 1974, Comarisov and Marshall60 developed Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). This technique allows mass spectrometric measurements at ultrahigh mass resolution (R = 100000-1000000), which is higher than that of any other type of mass spectrometer and has the highest mass accuracy at attomole detection limits. FTICR-MS is applied today together with soft ionization techniques, such as nano ESI (electrospray ionization) or MALDI (matrix assisted laser/desorption ionization) sources. 

Fourier transform ICR mass spectrometers together with any type of ion source, such as nanoESI, MALDI (or also an inductively coupled plasma ion source) permit mass spectrometric measurements to be performed at ultrahigh mass resolution (R = m/hm = 105—106) with a very low detection limit and the highest possible mass accuracy (Am = 10 3—10 4 Da). In addition, a high mass range is possible and FTICR-MS can be applied for MS/MS experiments.48 A comparison of different separation systems used in inorganic mass spectrometry is presented in Table 3.1. 

The analytically important features of Fourier transform ion cyclotron resonance (FT/ICR) mass spectrometry (1) have recently been reviewed (2-9) ultrahigh mass resolution (>1,000,000 at m/z. < 200) with accurate mass measurement even 1n gas chromatography/mass spectrometry experiments sensitive detection of low-volatility samples due to 1,000-fold lower source pressure than in other mass spectrometers versatile Ion sources (electron impact (El), self-chemical ionization (self-Cl), laser desorption (LD), secondary ionization (e.g., Cs+-bombardment), fast atom bombardment (FAB), and plasma desorption (e.g., 252cf fission) trapped-ion capability for study of ion-molecule reaction connectivities, kinetics, equilibria, and energetics and mass spectrometry/mass spectrometry (MS/MS) with a single mass analyzer and dual collision chamber. 

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