High mass, definition

Chlorambucil - there is no problem with the quantitation ion (at m/z 254), although the second ion proves to be a little difficult. While the ion at m/z 303 is the obvious choice, this is not very intense and therefore for samples containing small amounts of analyte the precision of measurement of this ion will be reduced and it may not be detectable at all levels at which the quantitation ion is observed. We could possibly consider the (M- -2) ion, as the combination o/m/z 254 (high mass, and therefore reasonable specificity), the presence of one chlorine, and the chromatographic retention time could be considered sufficient for definitive identification in those cases in which the intensity o/m/z 303 is insufficient. 

III. F.A.B.-M.S. OF High-Molecular-Weight Samples 1. Definition of High Mass... 

Ten years ago, it was easy to give a working definition of high mass. At that time, most mass spectrometers had a mass range of less than 1000 at... 

If delayed extraction increases the mass resolution without degradation of sensitivity compared with continuous extraction, it also has limitations. Indeed, delayed extraction complicates the mass calibration procedure. It can only be optimized for part of the mass range at a time and is less effective at high mass. Delayed extraction partially decouples ion production from the flight time analysis, thus improving the pulsed beam definition. However, calibration, resolution and mass accuracy are still affected by conditions in the source. For instance, in the usual axial MALDI-TOF experiments, optimum focusing conditions depend on laser pulse width and fluence, the type of sample matrix, the sample preparation method, and even the location of the laser spot on the sample. 

This method also suffers from mass limit restrictions, which for FAB is — 6000 amu with the definite probability of expanding these limits to the 12,500 amu range. Instrumentation capable of such high mass analysis has not been used to date for the sequence analysis of polynucleotides. 

A common question asked of the mass spectrometrist is how close in miz can two peaks at mJz = 1 000 or mIz = 20,000 be and still be distinguished with confidence The detailed answer is not as simple as one would like because it is dependent on the sample and instrument resolution. First, there are different definitions that exist for the resolving power of a mass spectrometer. A common definition, R = ml Am at mass m, is used in this chapter. The value of Amk is the measurement of the mass peak at full width at half maximum (FWHM). If the FWHM for the C monoisotopic peak for a 1000-amu peptide is 0.5 amu, then R = 2000, and for a 20,000-amu protein with the same FWHM, R = 40,000. For the preceding example, the isotope peaks would be distinguishable. In other words, for miz up to 10,000 amu, where z = 1, it is possible to obtain monoisotopic information with a mass spectrometer capable of resolution between 20,000 to 30,000. At high mass (>10,000 amu), however, most mass spectrometers can only acquire average molecular weight data, not monoisotopic data. The Fourier transform mass spectrometer is capable ofR= 1,000,000 at miz = 1000. 

At high-mass-transfer Peclet numbers, sketch the relation between average residence time divided by the chemical reaction time constant (i.e., r/co) for a packed catalytic tubular reactor versus the intrapeUet Damkohler number Aa, intrapeiiet for zeroth-, first-, and second-order irreversible chemical kinetics within spherical catalytic pellets. The characteristic length L in the definition of Aa, intrapeiiet is the sphere radius R. The overall objective is to achieve the same conversion in the exit stream for all three kinetic rate laws. Put all three curves on the same set of axes and identify quantitative values for the intrapeiiet Damkohler number on the horizontal axis. 

A rapid sampling method for direct aerosol analysis using FD-mass spectrometer has been described . In a predominantly inorganic aerosol three alkali metal cations and a number of cluster ions of intact salts have been identified under the conditions of high mass resolution (R 15,000, 10 per cent valley definition) using photographic registration. 

There is considerable information available in the hterature on the design of ejectors (steam jet ejectors, water jet pumps, air injectors, etc.) supported by extensive experimental data. Most of this information deals with its use as an evacuator and the focus is on ejector optimization for maximizing the gas pumping efficiency. The major advantage of the venturi loop reactor is its relatively very high mass transfer coefficient due to the excellent gas-liquid contact achieved in the ejector section. Therefore, the ejector section needs careful consideration to achieve this aim. The major mass transfer parameter is the volumetric liquid side mass transfer coefficient, k a. The variables that decide k a are (i) the effective gas-hquid interfacial area, a, that is related to the gas holdup, e. The gas induction rate and the shear field generated in the ejector determine the vine of and, consequently, the value of a. (ii) the trae liquid side mass transfer coefficient, k. The mass ratio of the secondary to primary fluid in turn decides both k and a. For the venturi loop reactor the volumetric induction efficiency parameter is more relevant. This definition has a built in energy... 

All forms of PBAs have many common requirements necessary to meet their prodnct definition requirements, although there will be significant variations in the product definition requirements for PBAs due to their specific form and application requirements. For example, the requirement for PBA flatness due to bow and twist may be different for a plug-in than for a mechanically mounted PBA. The requirements for the number and location of mounting fasteners for a mechanically mounted PBA will be different for a relatively thick MLB with low-mass components than for a simpler PB with high-mass components. 

Improving the mass resolution (definition is covered in Section 5.1.1.1.1) reduces this m/q spread, thereby allowing for the separation of secondary ion signals of similar (nominal) m/q ratios. Minimal spread is noted in the FT-ICR mass spectra shown in Figure 5.2(c) where an extremely High Mass Resolution (HMR) was used (Smith et al. 2013). 

Hgure 2.13 Definition of mass resolutions (a) 5 and 10% valley definition, (b) full width at half maximum and (c) mass resolution for pseudo high mass resolution... 

Previous theoretical kinetic treatments of the formation of secondary, tertiary and higher order ions in the ionization chamber of a conventional mass spectrometer operating at high pressure, have used either a steady state treatment (2, 24) or an ion-beam approach (43). These theories are essentially phenomenological, and they make no clear assumptions about the nature of the reactive collision. The model outlined below is a microscopic one, making definite assumptions about the kinematics of the reactive collision. If the rate constants of the reactions are fixed, the nature of these assumptions definitely affects the amount of reaction occurring. 

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