Fragmentation (mass spectrometry)

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. Fragmentation that occurs in tandem mass spectrometry experiments has been a recent focus of research, because this data helps facilitate the identification of molecules.

Mass spectrometry techniques

Fragmentation can occur in the ion source (in-source fragmentation) where it has been used with electron ionization to help identify molecules and, recently (2020), with electrospray ionization it has been shown to provide the same benefit in facilitating molecular identification. Prior to these experiments, electrospray ionization in-source fragmentation was generally considered an undesired effect however, electrospray ionization using Enhanced In-Source Fragmentation/Annotation (EISA) has been shown to promote in-source fragmentation that creates fragment ions that are consistent with tandem mass spectrometers. Tandem mass spectrometry-generated fragmentation is typically made in the collision zone (post-source fragmentation) of a tandem mass spectrometer. EISA and collision-induced dissociation (CID) among other physical events that impact ions are a part of gas-phase ion chemistry. A few different types of mass fragmentation are

collision-induced dissociation (CID) through collision with neutral molecule,

surface-induced dissociation (SID) using fast moving ions collision with a solid surface,

laser induced dissociation which uses laser to induce the ion formation,

electron-capture dissociation (ECD) due to capturing of low energy electrons,

electron-transfer dissociation (ETD) through electron transfer between ions,

negative electron-transfer dissociation (NETD),

electron-detachment dissociation (EDD),

photodissociation, particularly infrared multiphoton dissociation (IRMPD) using IR radiation for the bombardment and blackbody infrared radiative dissociation (BIRD) which use IR radiation instead of laser,

higher-energy C-trap dissociation (HCD), EISA, and

charge remote fragmentation.

Fragmentation reactions

Fragmentation is a type of chemical dissociation, in which the removal of the electron from the molecule results in ionization. Removal of electrons from either sigma bond, pi bond or nonbonding orbitals causes the ionization.