Quadrupole mass filter TOF

B magnetic sector E = electric sector Q = quadrupole mass filter ToF = time-of-flight mass spectrometer IT = ion trap FTICR = Fourier-transform ion-cyclotron resonance. 

ToFs can also be used in combination with other mass analysers. Both hybrid sector and quadrupole systems are available. oaToF-MS has been interfaced to a quadrupole mass filter and hexapole gas collision cell, such as to allow recording of mass spectra and product ion spectra with good mass resolution (ca. 10000), high sensitivity, high mass range (ca. 10 000 Da) and high mass accuracy (<5ppm) [177,178]. QqToFMS may be fitted with API sources with flow-rates from nL... 

Undoubtedly, the technique most suited to tackle polyatomic multichannel reactions is the crossed molecular beam (CMB) scattering technique with mass spectrometric detection and time-of-flight (TOF) analysis. This technique, based on universal electron-impact (El) ionization coupled with a quadrupole mass filter for mass selection, has been central in the investigation of the dynamics of bimolecular reactions during the past 35 years.1,9-11 El ionization affords, in principle, a universal detection method for all possible reaction products of even a complex reaction exhibiting multiple reaction pathways. Although the technique is not usually able to provide state-resolved information, especially on a polyatomic... 

Two types of mass analyzers have been used extensively in atmospheric applications quadrupole mass filters and time-of-flight (TOF) instruments. The use of ion traps is also being increasingly explored for this application. For the fundamental principles of mass... 

The complications just described can be minimized if there is greater selectivity in the ionization process, as is sometime possible when photoionization is used as the excitation mechanism. Because the ionization energy can be more precisely controlled, it is possible in selected cases to produce only the desired reactant-ion species, or at least to minimize production of other ions. As already noted in the earlier section on formation of excited ions, it is also possible to populate specific internal-energy states of some reactant ions by using a photoionization source. One of the earliest photoionization mass spectrometers used to study interaction of internally excited ions with neutrals was that constructed by Chupka et al.91 Such apparatuses typically incorporate a photon source (either a line or a continuum source) and an optical monochromator, which are coupled to the reaction chamber. Various types of mass analyzer, including sector type, time-of-flight (TOF), and quadrupole mass filters, have been used with these apparatuses. Chupka has described the basic instrumental configuration in some detail.854 Photoionization mass spectrometers employed to study interactions of excited ions with neutral species have also been constructed in several other laboratories.80,1144,142,143 The apparatus recently developed by LeBreton et al.80 is illustrated schematically in Fig. 7 and is typical of such instrumentation. 

Fig. 5 Schematic of a QTOF MS instrument. Ions formed in the source region are introduced into a quadrupole mass filter (Fig. 7) that separates ions based on mass-to-charge ratio (m/z). Selected ions are then transferred into the TOF MS for detailed analysis (i.e., high resolution capabilities). (Courtesy of Micromass, Manchester, UK.)...

Preferably, electrospray ionization (ESI) is used in combination with quadrupole mass filters [16,17], whereas MALDI is commonly used in combination with the time-of-flight (TOF) analyzer [18], The relatively simple construction of these two types of analyzers and the resulting price advantage has led to their replacing the traditional magnetic sector instruments as the workhorses of mass spectrometric analysis. A more recent development is the ion-cyclotron-resonance (ICR) analyzer [19] which can be used for both ES-and MALDI-ionization. 

Ion optics Ion traps, smaller TOF and quadrupole mass filter... 

In this ion trap/ion mobility/quadrupole/TOF-MS, the quadrupole mass filter was used to isolate a specific m/z value for coUisional activated dissociation and subsequent mass analysis of fragment ions. 

Linear Ion Trap-oa-TOF Instrument A useful alternative design combines a quadrupole linear ion trap (LIT) with an oa-TOF mass analyzer [62]. This instrument consists of a short rf quadrupole ion guide, a quadrupole mass filter that operates in the rf-only mode, and an oa-TOF mass analyzer. The quadrupole mass filter is operated as an LIT to serve as an ion-accumulation and precursor-ion selection device. The mass-selected precursor is activated via a resonant excitation mode in the LIT, while the TOF instrument provides high-speed mass analysis of the resulting product ions. MS experiments have also been demonstrated with this hybrid system. A combination of QIT with an oa-TOF mass analyzer has also proven to be an effective tandem MS system [63,64]. The QIT performs tasks similar to those performed by an LIT in the LIT-oa-TOF design (i.e., its functions are ion accumulation, mass separation, and ion activation. 

All the data reported here were acquired on a hybrid quadrupole/ion mobility/ orthogonal acceleration time-of-flight (oa-TOF) instrument (Synapt G2 HDMS, Waters Corp., Milford, MA). A schematic of the instrument is shown in Figure 8.1. Ions generated in the atmospheric pressure source enter the vacuum system and pass through an ion guide and quadrupole mass filter to the IMS section of the instrument, which comprises three ion guides. 

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