Spectrometer tandem-in-time mass

Appropriate use of RF and DC voltages means that some ions can be selectively retained and product ions generated. Some of these ions can then be selected and their product ions generated. In this manner, a fragmentation chain can be established. The ion trap is a typical tandem-in-time mass spectrometer, in which precursor and product ions are created and analysed in the same physical space ionisation and ion analysis, on the other hand, take place at different times ( MS/MS in time )- The operation can be repeated several times, making it possible to perform MS11. Ion trap mass spectrometry thus consists of ... 

One of the principle uses of the ion trap is as a tandem-in-time mass spectrometer. Ions with a particular m/z ratio formed in the ion trap, or injected into the trap from an external source, can be isolated by resonantly ejecting all other... 

In tandem-in-time mass spectrometers all operations take place within a single-ion storage device, but at different times. The most common tandem-in-time instrument is the quadrupole ion trap (QIT). The ongoing development of a higher-sensitivity counterpart, the linear ion trap (LIT), will presumably lead to an eclipsing of the QIT. 

The quadrupole ion fiap (QIT) has developed into a highly successful MS/MS device [49]. It is a tandem-in-time mass spectrometer, meaning that all steps of MS/MS are performed in the same space but with a temporal sequence. A typical... 

Discuss the major differences between a tandem-in-space mass spectrometer and a tandem-in-time mass spectrometer. Include the advantages and disadvantages... 

Multiple mass analyzers exist that can perform tandem mass spectrometry. Some use a tandem-in-space configuration, such as the triple quadrupole mass analyzers illustrated (Fig.3.9). Others use a tandem-in-time configuration and include instruments such as ion-traps (ITMS) and Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS or FTMS). A triple quadrupole mass spectrometer can only perform the tandem process once for an isolated precursor ion (e.g., MS/MS), but trapping or tandem-in-time instruments can perform repetitive tandem mass spectrometry (MS ), thus adding n 1 degrees of structural characterization and elucidation. When an ion-trap is combined with HPLC and photodiode array detection, the net result is a profiling tool that is a powerful tool for both metabolite profiling and metabolite identification. 

FT-ICR mass spectrometers belong to the tandem-in-time category of instruments. The stage of precursor ion selection (MSI) is accomplished by selectively storing the ions of interest, whereas all others are ejected by means of a suitably tailored excitation pulse, e.g., using the SWIFT technique. [206] FT-ICR mass spectrometers are also capable of MS . 

These are not the only types of tandem mass spectrometers. There are numerous configurations of instruments that are based on the type of ion separation and many new terms associated with these instrument types. For example, there are instruments known as ion traps. The ion trap is a device that can measure mass, fragment a selected mass (as could be done in a collision cell) and then measure the mass of the fragment. The product ion produced by this all in one device is the same product ion that would be produced in a tandem quadrupole instrument. However, there is only one mass analyzer that functions as both the collision cell and mass measuring device. These types of instruments are sometimes referred to as tandem mass spectrometers, but are not abbreviated as MS/MS. The MS/MS analysis is done by separating the analysis in time (tandem in time) rather than two devices separated in space. A more generic term is best suited. This term is MS , where the n represents... 

Tandem Mass Spectrometer An instrument capable of performing multiple mass (mjz) analyses. There are two major categories (1) tandem-in-space instruments (triple quadmpole and Q-TOF), (2) tandem-in-time instruments (QIT and FTICR). 

Trapping mass spectrometers can also be used as tandem mass spectrometers. Unlike beam-type mstruments, which are referred to as tandem in space, trapping mass spectrometers are tandem in time, meaning that ions are held in one region of space while the parent ion is selected and dissociated and the daughter ion analyzed sequentially in time. The ability to perform tandem mass spectrometry is inherent in the design of trapping mass spectrometers. Gen-... 

The types of tandem mass spectrometers capable of performing MS/MS experiments fall into two basic categories tandem in space and tandem in time. Tandem-in-space instruments have discrete mass analyzers for each stage of mass spectrometry examples include multisector, triple-quadru-pole, and hybrid instruments (instruments having mixed types of analyzers such as a magnetic sector and a quadrupole). Tandem-in-time instruments have only one mass analyzer where each stage of mass spectrometry takes place in the same analyzer but is separated in time via a sequence of events. Examples of this type of instrument include Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometers and quadrupole ion traps, described in Chapter 3. 

Tandcm-in-Time Spectrometers. Tandem-in-iime instruments form the ions in a certain spatial region and then at a later lime expel the unwanted ions and leave the selected ions to be dissociated and mass analyzed in the same spatial region. This process can be repeated many limes over to perform not only MS/MS experiments, but also MS/MS/MS and MS" experiments. Fourier transform ICR and quadrupole ion-trap instruments are well suited lor performing MS" cxperimenls. In principle, tandem-in-time spectrometers can perform M.S/MS experiments much more simply than tandem-in-space instruments because of the dilTiculty in providing different ion focal positions in the latter. Although tandem-in-time spectrometers can readily provide product ion scans, other scans, such as precursor ion scans and neui ral loss scans, are much more difficult to perform than they arc with tandem in space instruments. 

To date, all tandem mass spectrometry in oTOF mass spectrometers has occurred in the front-end injection optics. These instruments are usually called quadrupole time-of flight (QTOF) instruments, because they start with a series... 

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