Collision-induced dissociation
Encyclopedia
In Mass spectrometry
, Collision-induced dissociation (CID), referred to by some as collisionally activated dissociation (CAD), is a mechanism by which to fragment molecular ion
s in the gas phase. The molecular ions are usually accelerated by some electrical potential to high kinetic energy
and then allowed to collide with neutral molecules (often helium
, nitrogen
or argon
). In the collision some of the kinetic energy is converted into internal energy
which results in bond breakage and the fragmentation of the molecular ion into smaller fragments. These fragment ions can then be analyzed by a mass spectrometer.
CID and the fragment ions produced by CID are used for several purposes. Partial or complete structural determination can be achieved. In some cases identity can be established based on previous knowledge without determining structure. Another use is in simply achieving more sensitive and specific detection. By looking for a unique fragment ion you can detect a given molecule in the presence of other molecules of the same nominal molecular weight, essentially reducing the background and increasing the limit of detection.
mass spectrometer there are three quadrupole
s. The first quadrupole termed "Q1" can act as a mass filter and transmits a selected ion and accelerates it towards "Q2" which is termed a collision cell. The pressure in Q2 is higher and the ions collides with neutral gas in the collision cell and fragments by CID. The fragments are then accelerated out of the collsion cell and enter Q3 which scans through the mass range, analyzing the resulting fragments (as they hit a detector). This produces a mass spectrum
of the CID fragments from which structural information or identity can be gained. Many other experiments using CID on a triple quadrupole exist such as precursor ion scans that determines where a specific fragment came from rather than what fragments are produced by a given molecule.
SORI-CID (sustained off-resonance irradiation collision-induced dissociation) is a CID technique used in Fourier Transform Ion Cyclotron Resonance
mass spectrometry
which involves accelerating the ions in cyclotron motion (in a circle inside of an ion trap
) and then increasing the pressure resulting collisions that produce CID fragments.
Mass spectrometry
Mass spectrometry is an analytical technique that measures the mass-to-charge ratio of charged particles.It is used for determining masses of particles, for determining the elemental composition of a sample or molecule, and for elucidating the chemical structures of molecules, such as peptides and...
, Collision-induced dissociation (CID), referred to by some as collisionally activated dissociation (CAD), is a mechanism by which to fragment molecular ion
Ion
An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...
s in the gas phase. The molecular ions are usually accelerated by some electrical potential to high kinetic energy
Kinetic energy
The kinetic energy of an object is the energy which it possesses due to its motion.It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes...
and then allowed to collide with neutral molecules (often helium
Helium
Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...
, nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
or argon
Argon
Argon is a chemical element represented by the symbol Ar. Argon has atomic number 18 and is the third element in group 18 of the periodic table . Argon is the third most common gas in the Earth's atmosphere, at 0.93%, making it more common than carbon dioxide...
). In the collision some of the kinetic energy is converted into internal energy
Internal energy
In thermodynamics, the internal energy is the total energy contained by a thermodynamic system. It is the energy needed to create the system, but excludes the energy to displace the system's surroundings, any energy associated with a move as a whole, or due to external force fields. Internal...
which results in bond breakage and the fragmentation of the molecular ion into smaller fragments. These fragment ions can then be analyzed by a mass spectrometer.
CID and the fragment ions produced by CID are used for several purposes. Partial or complete structural determination can be achieved. In some cases identity can be established based on previous knowledge without determining structure. Another use is in simply achieving more sensitive and specific detection. By looking for a unique fragment ion you can detect a given molecule in the presence of other molecules of the same nominal molecular weight, essentially reducing the background and increasing the limit of detection.
Examples
In a triple quadrupoleQuadrupole
A quadrupole or quadrapole is one of a sequence of configurations of—for example—electric charge or current, or gravitational mass that can exist in ideal form, but it is usually just part of a multipole expansion of a more complex structure reflecting various orders of complexity.-Mathematical...
mass spectrometer there are three quadrupole
Quadrupole
A quadrupole or quadrapole is one of a sequence of configurations of—for example—electric charge or current, or gravitational mass that can exist in ideal form, but it is usually just part of a multipole expansion of a more complex structure reflecting various orders of complexity.-Mathematical...
s. The first quadrupole termed "Q1" can act as a mass filter and transmits a selected ion and accelerates it towards "Q2" which is termed a collision cell. The pressure in Q2 is higher and the ions collides with neutral gas in the collision cell and fragments by CID. The fragments are then accelerated out of the collsion cell and enter Q3 which scans through the mass range, analyzing the resulting fragments (as they hit a detector). This produces a mass spectrum
Mass spectrum
A mass spectrum is an intensity vs. m/z plot representing a chemical analysis. Hence, the mass spectrum of a sample is a pattern representing the distribution of ions by mass in a sample. It is a histogram usually acquired using an instrument called a mass spectrometer...
of the CID fragments from which structural information or identity can be gained. Many other experiments using CID on a triple quadrupole exist such as precursor ion scans that determines where a specific fragment came from rather than what fragments are produced by a given molecule.
SORI-CID (sustained off-resonance irradiation collision-induced dissociation) is a CID technique used in Fourier Transform Ion Cyclotron Resonance
Fourier transform ion cyclotron resonance
Fourier transform ion cyclotron resonance mass spectrometry, also known as Fourier transform mass spectrometry, is a type of mass analyzer for determining the mass-to-charge ratio of ions based on the cyclotron frequency of the ions in a fixed magnetic field...
mass spectrometry
Mass spectrometry
Mass spectrometry is an analytical technique that measures the mass-to-charge ratio of charged particles.It is used for determining masses of particles, for determining the elemental composition of a sample or molecule, and for elucidating the chemical structures of molecules, such as peptides and...
which involves accelerating the ions in cyclotron motion (in a circle inside of an ion trap
Ion trap
An ion trap is a combination of electric or magnetic fields that captures ions in a region of a vacuum system or tube. Ion traps have a number of scientific uses such as mass spectrometery and trapping ions while the ion's quantum state is manipulated...
) and then increasing the pressure resulting collisions that produce CID fragments.