Triple quadrupole mass analyser

Quadrupole mass analysers provide good reproducibility and represent a relatively small and low-cost system. Low-energy collision-induced dissociation (CID) MS/MS experiments are enabled in triple quadrupole and hybrid mass spectrometers and have efficient conversion of precursor to product. These spectra depend strongly on energy, collision gas, pressure, and other factors. Quadmpole mass... 

The triple quadrupole system consists basically of two quadrupole analysers (first and second quadrupole). The second quadrupole has only an R.F. voltage (without the D.C. component) and serves therefore as an ion focusing device [7]. The collision cell is located between the rods of this quadrupole. It has been found that when doing MS/MS with a tandem quadrupole mass analyser, an additional quadrupole focusing device is needed to focus the ions formed in the collision cell. 

A triple-quadrupole instrument (Q-qcoirQ) consists of two quadrupole mass analysers, connected by means of a collision cell, which is an RF-only... 

Figure 8 Curie-point pyrolysis MS-MS system pyrolysis products diffuses into the ion source where the ions are formed by electron-impact (El) ionization and analysed by a triple quadrupole mass analyser (Q1-Q3). Different modes of ion analysis (a) El spectrum of a pyrolysate (b) neutral loss spectrum (c) single ion spectrum and (d) collisionally induced dissociation spectrum of a parent ion...

Most thermospray interfaces have been fitted onto (triple) quadrupole mass analysers, although thermospray interfaces for magnetic sector instruments were commercially available as well. 

A triple-quadrupole mass spectrometer with an electrospray interface is recommended for achieving the best sensitivity and selectivity in the quantitative determination of sulfonylurea herbicides. Ion trap mass spectrometers may also be used, but reduced sensitivity may be observed, in addition to more severe matrix suppression due to the increased need for sample concentration or to the space charge effect. Also, we have observed that two parent to daughter transitions cannot be obtained for some of the sulfonylurea compounds when ion traps are used in the MS/MS mode. Most electrospray LC/MS and LC/MS/MS analyses of sulfonylureas have been done in the positive ion mode with acidic HPLC mobile phases. The formation of (M - - H)+ ions in solution and in the gas phase under these conditions is favorable, and fragmentation or formation of undesirable adducts can easily be minimized. Owing to the acid-base nature of these molecules, negative ionization can also be used, with the formation of (M - H) ions at mobile phase pH values of approximately 5-7, but the sensitivity is often reduced as compared with the positive ion mode. 

Different mass analysers can be combined with the electrospray ionization source to effect analysis. These include magnetic sector analysers, quadrupole filter (Q), quadrupole ion trap (QIT), time of flight (TOF), and more recently the Fourrier transform ion cyclotron resonance (FTICR) mass analysers. Tandem mass spectrometry can also be effected by combining one or more mass analysers in tandem, as in a triple quadrupole or a QTOF. The first analyzer is usually used as a mass filter to select parent ions that can be fragmented and analyzed by subsequent analysers. 

In addition to the diversity of ionisation techniques available, mass spectrometers offer a selection of mass analyser configurations. Of note are single (MS) and triple quadrupole (MS—MS) instruments, ion trap analysers (MS)n, time-of-flight (ToF) analysers, sector field analysers, and Fourier transform-ion cyclotron resonance (FTICR) instruments. 

In this instrument, the final stage of the triple quadrupole is replaced by an orthogonal time-of-flight (ToF) mass analyser, as shown in Figure 3.10. The configuration is typical of the latest generation of ToF instruments in which a number of reflectrons, in this case two, are used to increase the flight path of the ions and thus increase the resolution that may be achieved. 

Fig. 5 Statistical evaluation of LC-MS-based methods for tropane alkaloids referred in this chapter. (a) Relative frequency of ionization methods. +APCI positive atmospheric pressure chemical ionization, +ESI positive electrospray ionization, FAB fast atom bombardment, +TSP positive thermospray, (b) Relative frequency of scan modes used. MS full scan MS, MS/MS tandem mass spectrometry (product ion scan), MRM multiple reaction monitoring, SIM selected ion monitoring, (c) Relative frequency of mass analysers used. EBQtQ2 double focusing sector field mass spectrometer, IT ion trap, QqQ triple quadrupole, SQ single quadrupole. Considered publications were found by PubMed data-based search and references cited in these articles...

Whereas the interface produces analyte ions the mass analyser identifies the corresponding masses or may allow fragmentation for tandem-mass spectrometry (MS/MS or MS2) or multiple fragmentation (MS ). Single quadrupole (SQ), triple... 

All mass spectrometric analyses were carried out on a triple quadrupole mass spectrometer (TSQ-700) from Finnigan-MAT (San Jose, CA) equipp with an electrospray ion source (ESI) operating at atmospheric pressure. Mass spectra were recorded in the positive ion mode. The electrospray needle was operated at a differential of 3-4 kV, the conversion dynode was set to -15 V. The drying gas was nitrogen and the temperature was set to about 200 °C. A sheath flow of 2-methoxyethanol was delivered with 2 pJ/min and the nitrogen sheath gas was set at 50 psi. Samples were directly introduced into the source with a flow rate of 2 p.l/min. Scans were continuously taken every three seconds. 

Quadrupole mass filters are one of the most common and cost effective mass analyzers. Although they have limited mass resolution (Table 10.2) and are less sensitive than other mass analyzers, they are durable and suitable for high-throughput analyses. To perform a tandem mass analysis (MS/MS), a triple quadrupole MS is used in which three quadrupoles are placed in series to select, fragment, and analyze ions of interest. Quadrupole ion-trapping devices such as linear 2D ion traps are... 

These analysers are the same as those that suit GC-MS and LC-MS instruments. Tandem MS can also be carried out using suitable mass analysers such as the triple quadrupole (MS ) and ion trap (MS ). 

Various forms of tandem mass spectroscopy (MS/MS) have also been used in the analysis of biomolecules. Such instruments consist of an ionisation source (ESI or MALDI or other) attached to a first mass analyser followed by a gas-phase collision cell. This collison cell further fragments the selected ions and feeds these ions to a second mass detector. The final mass spectrum represents a ladder of fragment ions. In the case of peptides the collision cell usually cleaves the peptides at the amide bond. The ladder of resulting peptides reveals the sequence directly [496]. Thus, tandem MS instruments, such as the triple quadrupole and ion-trap instruments have been routinely applied in LC-MS/MS or ESI-MS/MS for peptide sequencing and protein identification via database searching. New configurations, which have been moving into this area include the hybrid Q-TOF [498], the MALDI-TOF-TOF [499] and the Fourier transform ion cyclotron resonance instruments [500]. 

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