Tandem Mass Spectrometry Breaks Down Selected Ions into Fragments

Tandem mass spectrometry occupies an important position in breaking down ions into fragments, which then reveal aspects of the chemical structure of the precursor ion.

In this post, the workflow of tandem mass spectrometry in this aspect is introduced in detail. ESI, MALDI and other techniques are used to ionize samples, in order to get a mixture of ions. And then selecting precursor ions of a specific mass-to-charge ratio, which then should be broken down to produce a product ions to be detected. And then the selectrion-fragmentation-detection sequence will be extended to the first-generation product ions furtherly. For instance, the selected product ions, which are generated in MS2, can be further fragmented to generate another group of product ions and other ions.

tandem MS

Instrumentation of tandem MS
Because of the three steps of selection-fragmentation-detection involved in tandem MS, researchers can realize the three steps in space or in time.

Tandem MS in space
There are many instruments included in typical tandem MS in space. They are QTOF, QqQ, hybrid ion trap/FTMS and so on.

QTOF(Quadrupole Time-of-flight)
In quadrupole time-of-flight, the precursor ions will be selected in the Quadrupole and then sent to the Collision cell for fragmentation. And after that, TOF mass spectrometry is used to detect the generated product ions.

QqQ(Triple Quadrupole)
Lining up three Quadrupoles, including Quad 1, Quad 2 and Quad 3) in a row, selecting precursor ions in Quad 1 and then sending it to Quad 2 for fragmentation. Product ions generated are then sent to Quad 3 for mass scanning.

Hybrid ion trap/FTMS
As for the hybrid ion trap/FTMS instruments, the precursor ions will be selected and dissociated in an external ion trap. The generated product ions will be detected in external trap by FTMS.

Tandem MS/MS in time
The ion trap and FT-ICR are included in the typical tandem-in-time MS/MS instruments.

These are some detailed information on how tandem MS works in breaking down selected ions to be dissociated.