Tandem mass spectrometry in time

Selected Reaction Monitoring (SRM) Data acquired from specific product ions corresponding to m/z selected precursor ions recorded via two or more stages of mass spectrometry. Selected reaction monitoring can be preformed as tandem mass spectrometry in time or tandem mass spectrometry in space. The term multiple reaction monitoring is deprecated [1],... 

Quadmpole ion traps (also referred to as Paul Traps ) can be used to generate product ion spectra. In fact, these instmments can offer MS" scans with n up to 10 [59] allowing for investigation of fragmentation mechanisms and for thorough stmctural elucidation. Since separation of precursor and product ion(s) occurs at the same place but temporally shifted, ion trap MS/MS is referred to as tandem mass spectrometry in time. ... 

There are two basic instrumental concepts for MS/MS. The first is tandem mass spectrometry in space (or tandem-in-space MS). In order to perform two consecutive mass-analyzing steps, two mass analyzers may be mounted in tandem. Thus, tandem-in-space refers to MS/MS instrumentation where product ion spectra are recorded using spatially separated m/z analyzers. Speedfic m/z separation is performed so that in one section of the instrument ions are selected, then dissociated in an intermediate region, and the products thereof are finally transmitted to a second analyzer for mass analysis (Fig. 9.1). All beam transmitting devices, e.g., multiple sector, ReTOF, TOF/TOF, QqQ, and QqTOF instruments follow this route to tandem MS (Fig. 9.2) [4]. The second approach, tandem mass spectrometry in time (or tandem-in-time MS), enploys a single m/z analyzer (QIT, LIT, FT-ICR) that may be operated by executing the discrete steps of ion selection, activation, and product ion analysis in the very same place but sequentially in time [4]. 

The acquisition and study of the spectra of selected precursor ions, or of precursor ions of a selected neutral mass loss. Structure selective target analyte quantitations use SRM/MRM data acquisition methods. MS/MS can be accomplished using beam instruments incorporating more than one analyser (tandem mass spectrometry in space, triple quadrupole analyzer) or in trap instruments (tandem mass spectrometry in time). 

Labadie P, Hill EM (2007) Analysis of estrogens in river sediments by liquid chromatography-electrospray ionisation mass spectrometry—comparison of tandem mass spectrometry and time-of-flight mass spectrometry. J Chromatogr A 1141 174-181... 

There are several ways to perform tandem mass spectrometry in an ion trap. Time-dependent rather than space-dependent tandem mass spectrometry occurs in the trap. The general sequence of operations is as follows ... 

Basically, a tandem mass spectrometer can be conceived in two ways performing tandem mass spectrometry in space by the coupling of two physically distinct instruments, or in time by performing an appropriate sequence of events in an ion storage device. Thus there are two main categories of instruments that allow tandem mass spectrometry experiments tandem mass spectrometers in space or in time. 

Tandem mass spectrometry or MS/MS is frequently used for structural elucidation of phytochemicals to provide more detailed information about the structure and composition of a molecule. This involves two mass spectral steps and fragmentation of the compound occurs between the steps. The two steps may be separated in space or in time depending on whether two distinct separation elements are used (space) or two different separations occur in the same place over time. As described previously, an IT analyzer can be used to successively fragment a molecule to provide MS" spectra, an example of separation in time. A triple quadrupole mass spectrometer is a form of tandem mass spectrometry in space in which two quadrupoles serve as mass filters while a third, positioned in the middle, allows for collision-induced dissociation. Triple quadrupoles are common in phytochemical analysis, and have been used to characterize phenolic compounds in fruit juices (Abad-Garcia et ah, 2009) and procyanidins and alkaloids in cocoa (Ortega et ah, 2010), among others. 

Boyd, R.K., Tandem mass spectrometry quadropole and hybrid instruments, Metftodi nzymo/. 193, 154-200, 1990 Jonscher, K.R. and Yates, J.R., 111, The quadrupole ion trap mass spectrometry — a small solution to a big challenge. Anal. Biochem. 244, 1-15, 1997 Chemushevich, I.V., Loboda, A.V., and Thomson, B.A., An introduction to quadrupole-time-of-flight mass spectrometry, J. Mass Spectrom. 36, 849-865, 2001 Ens, W. and Standing, K.G., Hybrid quadrapole/time-of-flight mass spectrometers for analysis of biomolecules. Methods Enzymol. 402,49-78, 2005 Payne, A.H. and GUsh, G.L., Tandem mass spectrometry in quadrupole ion trap and ion cyclotron resonance mass spectrometers. Methods Enzymol. 402, 109-148, 2005. 

Sleeman R., Bennett G., Davidson W. R., and Fisher W., The detection of illicit drugs and explosives in real-time by tandem mass spectrometry, in Proceedings of the contraband and cargo inspection technology international symposium, Washington, D.C., 57-63, 1992. 

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... 

IRMPD has a few advantages over SORI-CAD for tandem mass spectrometry in FTMS. First, the use of a collision gas is not necessary in IRMPD MS/MS this maintains optimal pressure in the analyzer cell and eliminates pumpdown time, facilitating its use for on-line... 

Multidimensional or hyphenated instmments employ two or more analytical instmmental techniques, either sequentially, or in parallel. Hence, one can have multidimensional separations, eg, hplc/gc, identifications, ms/ms, or separations/identifications, such as gc/ms (see CHROMATOGRAPHY Mass spectrometry). The purpose of interfacing two or more analytical instmments is to increase the analytical information while reducing data acquisition time. For example, in tandem-mass spectrometry (ms/ms) (17,18), the first mass spectrometer appHes soft ionization to separate the mixture of choice into molecular ions the second mass spectrometer obtains the mass spectmm of each ion. 

Tandem mass spectrometry (MS/MS) is a method for obtaining sequence and structural information by measurement of the mass-to-charge ratios of ionized molecules before and after dissociation reactions within a mass spectrometer which consists essentially of two mass spectrometers in tandem. In the first step, precursor ions are selected for further fragmentation by energy impact and interaction with a collision gas. The generated product ions can be analyzed by a second scan step. MS/MS measurements of peptides can be performed using electrospray or matrix-assisted laser desorption/ionization in combination with triple quadruple, ion trap, quadrupole-TOF (time-of-flight), TOF-TOF or ion cyclotron resonance MS. Tandem... 

Q-ToF-LC-MS-MS quadrupole time-of-flight mass analyser in combination with (high performance) liquid chromatography and tandem mass spectrometry... 

A further extension of the DFG S19 method was achieved when polar analytes and those unsuitable for GC were determined by LC/MS or more preferably by liquid chromatography/tandem mass spectrometry (LC/MS/MS). Triple-quadrupole MS/MS and ion trap MS" have become more affordable and acceptable in the recent past. These techniques provide multiple analyte methods by employing modes such as time segments, scan events or multiple injections. By improving the selectivity and sensitivity of detection after HPLC separation, the DFG S19 extraction and cleanup scheme can be applied to polar or high molecular weight analytes, and cleanup steps such as Si02 fractionation or even GPC become unnecessary. 

More recently, liquid chromatography/mass spectrometry (LC/MS) and liquid chromatography/tandem mass spectrometry (LC/MS/MS) have been evaluated as possible alternative methods for carfentrazone-ethyl compounds in crop matrices. The LC/MS methods allow the chemical derivatization step for the acid metabolites to be avoided, reducing the analysis time. These new methods provide excellent sensitivity and method recovery for carfentrazone-ethyl. However, the final sample extracts, after being cleaned up extensively using three SPE cartridges, still exhibited ionization suppression due to the matrix background for the acid metabolites. Acceptable method recoveries (70-120%) of carfentrazone-ethyl metabolites have not yet been obtained. 

MS detection does not necessarily require as highly resolved GC separations as in the case of selective detectors because the likelihood of an overlapping mass spectral peak among pesticides with the same retention time is less than the likelihood of an overlapping peak from the same element. Unfortunately, this advantage cannot always be optimized because SIM and current gas chromatography/tandem mass spectrometry (GC/MS/MS) methods, it is difficult to devise sequential SIM or MS/MS retention time windows to achieve fast GC separations for approximately > 50 analytes in a single method. 

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