Tandem collision process

Tandem mass spectrometry summarizes the numerous techniques where mass-selected ions (MSI) are subjected to a second mass spectrometric analysis (MS2). [111,112] Dissociations in transit through the mass analyzer may either occur spontaneously metastable. Chaps. 2.7.1, 2.8.2) or can result from intentionally supplied additional activation, i.e., typically from collisions with neutrals. Below, we will chiefly discuss the collision process as such and its consequences for the further fate of the ions. Instrumental aspects of tandem MS are included in Chap. 4 and applications are presented in Chaps. 7-12. 

Figure 9 Product ion spectra resulting from 25 eV collisions of the pyrazine molecular ion (mlz 80) with (A) a D-SAM surface and (B) an F-SAM surface. Reproduced with permission from Winger BE, Laue H-J, Homing etal, (1992) Hybrid BEEQ tandem mass spectrometer for the study of ion/surface collision processes Review of Scientific Instruments 63 5613-5625.

R. S. Johnson, S. A. Martin, K. Biemann, J. T. Stults, and J. T. Watson, Novel Fragmentation Process of Peptides by Collision-Induced Decomposition in a Tandem Mass Spectrometer Differentiation of Leucine and Isoleucine. Anal. Chem., 59(1987) 2621-2625. 

Fig. 11.16. Representation of three tandem mass spectrometry (MS/MS) scan modes illustrated for a triple quadrupole instrument configuration. The top panel shows the attributes of the popular and prevalent product ion CID experiment. The first mass filter is held at a constant m/z value transmitting only ions of a single mlz value into the collision region. Conversion of a portion of translational energy into internal energy in the collision event results in excitation of the mass-selected ions, followed by unimolecular dissociation. The spectrum of product ions is recorded by scanning the second mass filter (commonly referred to as Q3 ). The center panel illustrates the precursor ion CID experiment. Ions of all mlz values are transmitted sequentially into the collision region as the first analyzer (Ql) is scanned. Only dissociation processes that generate product ions of a specific mlz ratio are transmitted by Q3 to the detector. The lower panel shows the constant neutral loss CID experiment. Both mass analyzers are scanned simultaneously, at the same rate, and at a constant mlz offset. The mlz offset is selected on the basis of known neutral elimination products (e.g., H20, NH3, CH3COOH, etc.) that may be particularly diagnostic of one or more compound classes that may be present in a sample mixture. The utility of the two compound class-specific scans (precursor ion and neutral loss) is illustrated in Fig. 11.17.

Johnson R.S., Martin S.A., Biemann K., Stulz J.T., and Watson J.T. (1987), Novel fragmentation process of peptides by collision-induced decomposition in a tandem mass spectrometer differentiation of leucine and isoleucine, Anal. Chem. 59, 2621-2625. 

Main processes in tandem mass spectrometry (MS/MS). CID stands for collision-induced dissociation, as occurs when an inert gas is present in the collision cell. 

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