What is fragmentation process of molecular ion?
In mass spectrometry, fragmentation is the dissociation of energetically unstable molecular ions formed from passing the molecules in the ionization chamber of a mass spectrometer. The fragments of a molecule cause a unique pattern in the mass spectrum.
What causes fragmentation in mass spectrometry?
Fragmentation occurs when energetically unstable molecular atoms dissociate (either through homolytic or heterolytic cleavage) as they pass through the ionization chamber of a mass spectrometer.
What happens when fragmentation of pentane?
All sorts of fragmentations of the original molecular ion are possible – and that means that you will get a whole host of lines in the mass spectrum. For example, the mass spectrum of pentane looks like this: With a compound, each line represents a different fragment produced when the molecular ion breaks up.
What causes the line at m/z 57?
The base peak, at m/z=57, is due to the [CH3CH2CO]+ ion. We’ve already discussed the fragmentation that produces this. The more stable an ion is, the more likely it is to form. The more of a particular ion that is formed, the higher will be its peak height.
What is molecular fragmentation?
Molecular fragmentation (mass spectrometry), or molecular dissociation, occurs both in nature and in experiments. It occurs when a complete molecule is rendered into smaller fragments by some energy source, usually ionizing radiation.
What does the peak at m/z 59 represents?
When R2 = CH3, observe m/z 58. When R2 = C2H5, observe m/z 72, etc. Small peaks at m/z 31, 45, and 59 indicate the presence of oxygen in the compound. Also, the mass spectra of aldehydes exhibit peaks at m/z values representing the losses of 28 and 44 from the molecular ion.
What is a fragment ion peak?
A term defined in the context of mass spectrometry as the charged product of an ion dissociation. A fragment ion may be stable or dissociate further to form other charged fragment ions and neutral species of successively lower mass.
What factors affect fragmentation?
Basic fragmentation types, rules and factors influencing it
- Cleavage of σ bond.
- Cleavage of 2σ bond (rearrangements)
- Cleavage of Complex rearrangements.
How do you know which ion is responsible for the peak?
Look for the peak with the highest value for m/z, and that value is the relative formula mass of the compound. There are, however, complications which arise because of the possibility of different isotopes (either of carbon or of chlorine or bromine) in the molecular ion.
What are B and Y ions?
For a given peptide sequence, the B ions are the product when the charge is retained on the N-Terminus (i.e. at the beginning of the sequence) and the Y ions the product when the charge is retained at the C-Terminus (i.e. at the end of the sequence).
What is the M 1 peak?
The M+1 peak is caused by the presence of the 13C isotope in the molecule. That means that 1 in every 100 of the molecules will have a mass of 17 (13 + 4) rather than 16 (12 + 4). The mass spectrum will therefore have a line corresponding to the molecular ion [13CH4]+ as well as [12CH4]+.
What is the molecular ion peak?
The molecular ion peak is both an important reference point and is integral in identifying an unknown compound. Even without a CI spectrum of the compound, the mass spectrum provides some information that can assist in ruling out potential masses as the molecular ion.
How are D and w ions used in peptide fragmentation?
A useful feature of d and w ions is that they enable the isobaric residues leucine and isoleucine to be differentiated. In low energy CID (i.e. collision induced dissociation in a triple quadrupole or an ion trap) a peptide carrying a positive charge fragments mainly along its backbone, generating predominantly b and y ions.
How can you tell if a fragment is an ion?
Fragments will only be detected if they carry at least one charge. If this charge is retained on the N terminal fragment, the ion is classed as either a, b or c. If the charge is retained on the C terminal, the ion type is either x, y or z. A subscript indicates the number of residues in the fragment.
Which is the ion fragment of fentanyl pattern 3A?
In the case of fentanyl, cleavage of the amide C-N bond of ion 202, Pattern 3A, yields ion fragment 146.
What makes the MW equal to the tropylium ion?
The presence of 91, the tropylium ion, in the spectra of fentanyl-like compounds strongly suggests a phenethyl group. In such cases, the MW of the compound will be equal to the BP plus 91.