Trapping quadrupole

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... 

Tandem mass spectrometry (MS-MS) uses more than one mass analyzer for structural and sequencing studies that have been found very useful for anthocyanin characterization. These mass analyzers may be of the same type (triple or quadru-poie)85,86 Qj. such as ion trap quadrupole, - and quadrupole-time-of-flight... 

Three-dimensional quadrupole ion trap Quadrupole (RF) ion traps are the newest of the commercially available mass analyzers, despite having been invented at about the same time as the quadrupole mass filter, nearly 50 years ago. The Paul ion trap... 

Various mass spectrometer configurations have been used for the detection of explosives, such as ion traps, quadrupoles and time-of flight mass analyzers and combinations as MS/MS systems. The ionization method is usually APCI with corona discharge [24, 25]. An example is given in Figure 20, which shows the schematic diagram of an explosive mass spectrometer detector [25]. It is based on an ion trap mass analyzer, an APCI source with corona discharge and a counter-flow introduction (CFI) system. The direction of the sample gas flow introduced into the ion source is opposite to that of the ion flow produced by the ion source. 

Once a targeted list is assembled, the appropriate LC-MS instrument can be set up to acquire both MS and MS/MS data (or MS" data for traps) in an automated fashion. The MS/MS acquisitions would only be triggered by detection of a targeted precursor ion (from the list) at a minimum specified intensity. Linear ion trap quadrupole instruments are increasingly popular for this type of work (Hopfgartner and Zell, 2005) and are discussed in Chapter 3 of this book. 

Various mass spectrometer configurations have been used for the detection of explosives, such as ion traps, quadrupoles, and time-of-flight (TOF) analyzers and tandem mass spectrometer (MS/MS) combinations. Also, various modes of ionization have been employed, depending on the specific application in the detection of explosives. 

Vallverdu-Queralt, A. Jauregui, O. Medina-Remon, A. Andres-Lacueva, C. Lamuela-Raventos, R.M. 2010. Improved characterization of tomato polyphenols using liquid chromatography/electrospray ionization linear ion trap quadrupole Orbitrap mass spectrometry and liquid chromatography/electrospray ionization tandem mass spectrometry. Rapid Comm. Mass Spectrom. 24 2986-2992. 

Traditional detectors (i.e., FID electron capture detector, BCD nitrogen-phosphorous detector, NPD) supply only retention data. However, in many cases this is not enough for proper identification of analytes. Application of GC coupled with an MS detector gives much more information (i.e., the mass spectmm of each compound). GC-MS is a well known and frequently used technique that combines the highly effective separation of GC with the high sensitivity and selectivity of MS. Moreover, improvements in analytical instruments based on different types of mass analyzers (ion trap, quadrupole, and TOF) and the development of hybrid Q-TOF has enhanced the analytical capabilities of modem hardware. Different kinds of mass spectrometers are presented in Table 14.2 [119]. 

Another approach to mass analysis is based on stable ion trajeetories in quadrupole fields. The two most prominent members of this family of mass spectrometers are the quadrupole mass filter and the quadmpole ion trap. Quadrupole mass filters are one of the most eommon mass speetrometers, being extensively used as detectors in analytical instmments, especially gas chromatographs. The quadmpole ion trap (whieh also goes by the name quadmpole ion store, QUISTOR , Paul trap, or just ion trap) is fairly new to the physieal chemistry laboratory. Its early development was due to its use as an inexpensive alternative to tandem magnetic sector and quadmpole filter instmments for analytieal analysis. It has, however, started to be used more in the chemical physics and physical chemistry domains, and so it will be deseribed in some detail in this section. 

ICR trap (10 ) > double sector (10 ) > time-of-flight (10 -10 = quadrupole ion trap > quadrupole (10 ) magnetic sector >electric sector (<10 ) ... 

The role of the mass analyzer is to separate ions according to their miz values and to focus and transfer these ions onto a detector, or into a collision cell in multianalyzer instruments (see later). The mass analyzer is the heart of all mass spectrometers (block 3 in Figure 1.2). The choice of which analyzer to use is critical as it affects multiple aspects of the data generated, including mass resolution, mass measurement accuracy, and available dynamic range. There are several types of analyzer quadru-pole (Q), ion trap (quadrupole (QIT) or linear (LIT) ion trap), time-of-flight (TOF),... 

A mass analyzer separates and mass-analyzes the ionic species. Magnetic and/or electric fields are used in mass analyzers to control the motion of ions. A magnetic sector, quadrupole, time-of-fiight, quadrupole ion trap, quadrupole linear ion trap, orbitrap, and Fourier transform ion cyclotron resonance instrument are the most common forms of mass analyzers currently in use (discussed in Chapter 3). 

First, if a multiple mass analyzer instrument is used, the pseudomolecular ion can be colHded with a stream of gas to generate collisionally induced dissociation (CID) and the formation of structurally significant fragment ions. MS/MS with selected reaction monitoring in a triple quadrupole is the method of choice for quantitation. Structure determination or confirmation is done by means of any of the available MS/MS fragmentation techniques triple quadrupole, ion trap, quadrupole-TOF, or FT-ICR. 

One of the latest mass analyzer is the linear-trap quadrupole (LTQ) Orbitrap mass spectrometer. In this, the commercial LTQ is coupled with an ion trap, developed by Makarov [73, 74]. Due to the resolving power (between 70000 and 800000) and the high mass accuracy (2-5 ppm), Orbitrap mass analyzers, for example, cab be used for the identification of peptides in protein analysis or for metabolomic studies. In addition, the selectivity of MS/MS experiments can be greatly improved. However, the coupling is not useful with UHPLC for rapid chromatographic pre-separation, as the data acquisition rate is too low for a reproducible integration of the narrow signals produced with UHPLC. 

Recently introduced tandem mass spectrometers, having both features, such as quad-rupole linear ion trap (QqLIT, LTQ or Q-trap), quadrupole time-of-fiight (QqTOF), LTQ-Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS), and LTQ-Orbitrap, and so on, have allowed for the development of several new methods for acrylamide detection [107,108]. 

Figure 6.16 Representations of a Paul ion trap (quadrupole ion trap), (a) Photograph of a trap cut in half through a plane containing the axis of cylindrical symmetry (z-axis). The physical size of the device is generally of the order of 1 cm within the trap cavity, (b) Schematic diagram of the cross-section. Reproduced from March, J. Mass Spectrom. 32, 351 (1997), with permission of John wiley Sons, Ltd.

TABLE 16.2 ESI and APCI Method Parameters for Linear and Ion Trap Quadrupole Mass Spectrometer Analysis by Direct Infusion... 

IMS is commonly coupled with a Unear time-of-flight (TOP) analyzer for the molecule separation and detection of proteins and reflector TOP analyzers for peptides. Ion trap quadrupole, TOP/TOP, and quadrupole TOP analyzers are typically used for drugs, metabolite, and other low MW analytes because of their MS/MS capabilities, providing high sensitivity in the presence of a complex matrix background (58). 

Interaction with electromagnetic fields linear ion-trap quadrupole... 

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