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A mass spectrum is a histogram plot of intensity vs. mass-to-charge ratio (m/z) in a chemical sample, [1] usually acquired using an instrument called a mass spectrometer. Not all mass spectra of a given substance are the same; for example, some mass spectrometers break the analyte molecules into fragments ; others observe the intact molecular ...
Mass spectral interpretation is the method employed to identify the chemical formula, characteristic fragment patterns and possible fragment ions from the mass spectra. [ 1 ] [ 2 ] Mass spectra is a plot of relative abundance against mass-to-charge ratio.
In mass spectrometry, fragmentation is the dissociation of energetically unstable molecular ions formed from passing the molecules mass spectrum.These reactions are well documented over the decades and fragmentation patterns are useful to determine the molar weight and structural information of unknown molecules.
ECD produces significantly different types of fragment ions (although primarily c- and z-type, b-ions have been identified in ECD [9]) than other MS/MS fragmentation methods such as electron-detachment dissociation (EDD) (primarily a and x types), [10] [11] [12] collision-induced dissociation (CID) (primarily b [13] and y type) and infrared ...
Electron-capture dissociation (ECD) was developed in 1998 to fragment large proteins for mass spectrometric analysis. [7] Because ECD requires a large amount of near-thermal electrons (<0.2eV), originally it was used exclusively with Fourier transform ion cyclotron resonance mass spectrometry (FTICR), the most expensive form of MS instrumentation. [8]
Table 1. Mass of amino acid fragment ions [4] [13] For interpretation, [14] first, look for single amino acid immonium ions (H 2 N + =CHR 2). Corresponding immonium ions for amino acids are listed in Table 1. Ignore a few peaks at the high-mass end of the spectrum. They are ions that undergo neutral molecules losses (H 2 O, NH 3, CO 2, HCOOH ...
The defining characteristic of an energy-based molecular fragmentation method is that the molecule (also cluster of molecules, or liquid or solid) is broken up into a set of relatively small molecular fragments, in such a way that the electronic energy, , of the full system is given by a sum of the energies of these fragment molecules:
This process allows for the study of fragments that are useful in structural elucidation by tandem mass spectrometry. For example, the Q 1 may be set to 'filter' for a drug ion of known mass, which is fragmented in q 2. The third quadrupole (Q 3) can then be set to scan the entire m/z range, giving information on the intensities of the ...