In Mass spectrometry, collision-induced dissociation (CID), refered to by some as collisionally activated dissociation (CAD), is a mechanism by which to fragment molecular ions in the gas phase. The molecular ions are usually accelerated by some electrical potential to high kinetic energy in the vacuum of a mass spectrometer and then allowed to collide with neutral gas 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. Mass spectrometry is a technique for separating ions by their mass-to-charge (m/z) ratios. ... An ion is an elementary particle or system of elementary particles with a net electric charge. ... Acceleration is the time rate of change of velocity, and at any point on a v_t graph, it is given by the gradient of the tangent to that point In physics, acceleration (symbol: a) is defined as the rate of change (or time derivative) of velocity. ... Electrical potential is the potential energy per unit charge associated with a static (time-invariant) electric field, also called the electrostatic potential or the electric potential, typically measured in volts. ... Kinetic energy (also called vis viva, or living force) is energy possessed by a body by virtue of its motion. ... Mass spectrometry is a technique for separating ions by their mass-to-charge (m/z) ratios. ... General Name, Symbol, Number helium, He, 2 Chemical series noble gases Group, Period, Block 18, 1, s Appearance colorless Atomic mass 4. ... General Name, Symbol, Number nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15, 2, p Appearance colorless Atomic mass 14. ... General Name, Symbol, Number argon, Ar, 18 Chemical series noble gases Group, Period, Block 18, 3, p Appearance colorless Atomic mass 39. ... The internal energy of a system (abbreviated E or U) is the total kinetic energy due to the motion of molecules (translational, rotational, vibrational) and the total potential energy associated with the vibrational and electric energy of atoms within molecules or crystals. ... Mass spectrometry is a technique for separating ions by their mass-to-charge (m/z) ratios. ...

CID and the fragment ions produced by CID are used for several purposes. Partial or complete structural determination can be achieved. In some cases indentity can be established based on previous knowledge without determining structure. Another use is in simply acheiving more sensitive and specific detection. By looking for a very unique fragment ion you can detect a given molecule in the presence of other molecules of the same nominal molecular mass, essentially reducing the background and increasing the limit of detection. In science, a molecule is the smallest particle of a pure chemical substance that still retains its chemical composition and properties. ... The molecular mass of a substance (less accurately called molecular weight and abbreviated as MW) is the mass of one molecule of that substance, relative to the unified atomic mass unit u (equal to 1/12 the mass of one atom of carbon-12). ...

CID is used as part of tandem mass spectrometry for many experiments in proteomics. Mass spectrometry is a technique for separating ions by their mass-to-charge (m/z) ratios. ... From Latin ex- + -periri (akin to periculum attempt). ... Proteomics is the large-scale study of proteins, particularly their structures and functions. ...

Examples

In a triple quadrupole mass spectrometer there are three quadrupole mass analyzers. 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 collide 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. Alongside Time of Flight, the quadrupole mass analyzer is one type of mass analyzer used in mass spectrometry. ... The Mass spectrum of any substance is the distribution of matter according to atomic and/or molecular masses that can be found when a sample of the substance is tested. ...

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 in collisions that produce CID fragments. AFter the SORI-CID process is complete pressure is reduced back to high vacuum and the analysis of the fragment ions is performed as usual. Fourier Transform Ion Cylotron Resonance, also known as Fourier Transform Mass Spectrometry, is a type of mass analyzer (or mass spectrometer) for determining the mass to charge ratio (m/z) of ions based on the cyclotron frequency of the ions in a magnetic field. ... Mass spectrometry is a technique for separating ions by their mass-to-charge (m/z) ratios. ... An ion trap is a combination of electric or magnetic fields that captures ions in a region of a vacuum system or tube. ...

External Links

• CAD vs. CID

• MS Terms Wiki definition