Tandem MS on TOF Instruments

Tandem mass spectrometry or MS/MS summarizes the numerous techniques where mass-selected ions (MSI) are subjected to a second mass spectrometric analysis (MS2). [53,54] Ion 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. The methods to activate or react otherwise stable ions in he field-free region (FFR) between MSI and MS2 are discussed in Chap. 2.12 and applications of MS/MS on TOF instruments are shown in Chaps. 10-12. 

In order to perform two consecutive mass-analyzing steps, two mass analyzers may be mounted in tandem. This technique is applied with beam transmitting devices, i.e., TOF, sector and quadrupole analyzers can be combined that way tandem-in-space, Fig. 4.15). Alternatively, a suitable mass analyzer may be operated by combining selection, activation, and analysis in the very same place. Quad-mpole ion trap (QIT) and ion cyclotron resonance (ICR) instruments can perform such tandem-in-time experiments. 

The linestyles indicate --- stable precursor ions,---transmitted ions, and fTTTTrn non- 

Methods for the detection of metastable ion dissociations in ReTOF-MS in combination with secondary ion mass spectrometry (SIMS) and Cf plasma desorption ( Cf-PD, Chap. 9.5.2) mass spectrometry were known before the advent of MALDI. [56-59] 

Consider an ion mi decomposing in transit through a field-free region. Its kinetic energy is then distributed among the product ion m.2 and the neutral fragment n according to their relative contribution to the mass of the precursor ion 

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