Quadrupole analyzers

Q/TOF, used for two mass analyzers (quadrupole and time-of-flight) used in combination QQQ (or QqQ)- a triple quadrupole analyzer (if q is used, it means the central quadrupole is also a collision cell)... 

The central transport chamber is an 80-cm-diameter stainless steel vessel, and is pumped by a 1000-1/s turbomolecular pump, which is backed by a small (501/s) turbomolecular pump to increase the compression ratio for hydrogen, and by a 16-m /h rotating-vane pump. UHV is obtained after a bake-out at temperatures above 100°C (measured with thermocouples at the outside surface) of the whole system for about a week. A pressure in the low 10 " -mbar range is then obtained. With a residual gas analyzer (quadrupole mass spectrometer, QMS) the partial pressures of various gases can be measured. During use of the system, the pressure in the central chamber is in the low 10 -mbar range due to loading of samples. Water vapor then is the most abundant species in the chamber. 

Like sector analyzers, quadrupole analyzers are well suited for continuous ion sources such as ESI, but are not well-suited for pulsed ionization methods. Quadmpole mass spectrometers are generally substantially cheaper and smaller than sector instruments and Qq-TOFs. They are very often used in combination with GC and LC, and single or triple quadmpole mass filters are very common benchtop instruments for routine measurements. 

Fig. 1.18 Schematic of a triple quadrupole instrument. Stage qO focusing quadrupole Ql, Q3 mass analyzing quadrupoles q2 collision cell. In the present configuration the collision energy (CE) is determined by the potential difference between qO and q2.

An impressive diversity of mass analyzers are utilized in modem analytical instrumentation. An overview of the common mass spectrometer analyzers follows, with particular emphasis on linear quadrupole mass analyzers, quadrupole ion traps, and time-of-flight mass analyzers, as they arguably constitute the quantitative MS workhorses of the pharmaceutical industry. The description of alternate analyzer systems should provide a framework in which the utility of these three particular systems provides the most cost-effective analytical mass spectrometer systems for pharmaceutical analysis. 

Quadrupole ion trap mass analyzers merge the trapping characteristics of the ICR with the physical principles of the linear quadrupole mass analyzer. Quadrupole ion traps produce time-dependent spectra with excellent sensitivity and tandem mass spectrometry capabilities, but unlike the ICR they provide these ion trapping characteristics with physically smaller and considerably less expensive instrumentation, giving them a reputation as a powerful and accessible tool for both qualitative and quantitative mass spectrometry [43-47]. The capability of quadrupole ion traps to be configured with either internal and external ionization sources has expanded their utility for modem analytical applications [48—52]. 

FIGURE 8.12 Schematic of triple quadrupole instrument, Qi and Q3 mass analyzing quadrupoles, q2 collision cell. 

Quadrupole mass filters consist of four parallel rods, illustrated in Figure 2. In such instruments, mass selection depends on ion motion resulting from simultaneously applied DC and RF electric fields. Scanning is accomplished by systematically changing the field strengths, thereby changing the miz value that is transmitted through the analyzer. Quadrupole mass... 

PeikinElmer uses a patented scanning quadrupole-based collision/reaction cell, called a universal cell, which can operate with collision/KED or reactive gas. The scanning quadrupole in the cell removes side reaction product and new interferences, so that only the analyte passes to the analyzing quadrupole. 

Mass analyzer quadrupole (VSW mass analyst quadrupole). 

MS was first successfully applied to analysis of intact microor nisms more than 40 years ago (Anhalt and Fenselau 1975). These efforts have expanded and have been particularly significant after the introduction of the soft ionization MS techniques—matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI) (Perm et al. 1989 Tanaka 2003 Karas andHillenkamp 1988). Both techniques (recognized by the Nobel Prize in Chemistry in 2002) allow the ionization and transfer into vacuum of large, intact, nonvolatile biomolecules, such as proteins. Various types of mass analyzers—quadrupole, ion trap, time-of-flight (TOF)— have been coupled to both MALDI and ESI ion sources, allowing multiple stages (tandem) MS to be performed for structure elucidation of analytes of interest. All these instrumental developments have allowed MS to become a well-established... 

Fig. 6.7. The Lausanne photofragment-spectrometer for measuring spectra of cold biomolecular ions as well as their clusters with solvent molecules. In the center of the tandem quadrupole mass spectrometer is a 22-pole ion trap which can be cooled to temperatures below 10 K. The ions of interest are produced by an electrospray source, mass-selected in a quadrupole, and then injected into the trap where they are cooled via collisions with cold helium. After irradiating the ions with IR and/or UV laser pulses, the contents of the trap are ejected and sent through an analyzing quadrupole before being detected. Spectra are generated by monitoring the appearance of a particular fragment ion mass as a function of the laser wave length.

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