Infrared multiphoton dissociation

Infobox chemical analysis
name = Infrared multiphoton dissociation


caption =
acronym = IRMPD
classification =
analytes =
manufacturers =
related = Blackbody infrared radiative dissociation
Electron capture dissociation
Collision-induced dissociation
hyphenated =

Infrared multiphoton dissociation (IRMPD) is a technique used in mass spectrometry to fragment molecules in the gas phase usually for structural analysis of the original (parent) molecule. cite journal | author = Little DP, Speir JP, Senko MW, O'Connor PB, McLafferty FW | title = Infrared multiphoton dissociation of large multiply charged ions for biomolecule sequencing | journal = Anal. Chem. | volume = 66 | issue = 18 | pages = 2809–15 | year = 1994 | pmid = 7526742 | doi = ]

How it works

An infrared laser is directed through a window into the vacuum of the mass spectrometer where the ions are. The mechanism of fragmentation involves the absorption by a given ion of multiple infrared photons. The parent ion becomes excited into more energetic vibrational states until a bond(s) is broken resulting in gas phase fragments of the parent ion.

IRMPD is most often used in Fourier transform ion cyclotron resonance mass spectrometry.cite journal | author = Laskin J, Futrell JH | title = Activation of large ions in FT-ICR mass spectrometry | journal = Mass spectrometry reviews | volume = 24 | issue = 2 | pages = 135–67 | year = 2005 | pmid = 15389858 | doi = 10.1002/mas.20012]

IRMPD spectroscopy

By applying intense tunable IR lasers, like IR-OPOs or IR free electron lasers, the wavelength dependence of the IRMPD yield can be studied. This IRMPD spectroscopy allows for the measurement of vibrational spectra of (unstable) species that can only be prepared in the gas phase. Such species include molecular ions but also neutral species that can be gently ionized after interaction with the IR light for their mass spectrometric detection.

ee also

* Infrared spectroscopy
* Blackbody infrared radiative dissociation
* Electron capture dissociation
* Collision-induced dissociation is another, more common, method to fragment gas phase ions.

References