Mass analyzers orthogonal acceleration

Fig. 11.13. Diagram of a TOF mass analyzer (with reflectron). Ions enter from an external source and are accelerated (orthogonally) by the pusher electrode toward the reflectron. The reflectron (ion mirror) retards, reverses and reaccelerates the ions back toward the micro-channel plate detector.

Laser desorption intrinsically is a pulsed ionization process, which is therefore ideally combined with time-of-flight (TOF) analyzers (Chap. 4.2). [16,49] Ever since the first MALDI experiments, MALDI and TOF have been forming a unit, and the majority of MALDI applications are MALDI-TOF measurements. Vice versa, it was the success of MALDI that pushed forth the tremendous delevopment of TOF mass analyzers. More recently, MALDI has also been adapted to orthogonal acceleration TOF analyzers. [147]... 

Hieftje and co-workers first reported a design for ICP-ToF mass spectrometric systems with both orthogonal acceleration (oa) and axial acceleration (aa) geometry.39 11 The different experimental setups of ICP-ToF mass spectrometers with orthogonal and axial acceleration are compared in Figures 5.10 and 5.11. Both instruments possess a time-of-flight analyzer with a reflectron to improve the mass resolution. 

For ions produced in the gas phase, typical of most ion sources coupled to separation systems, a combination of quadrupole injection and an orthogonal accelerator produces a focused ion beam with a small kinetic energy distribution from virtually any ion source. Early interfaces between the ion source and mass analyzer merely provided... 

Time-of-fiight instruments are configured as either a stand-alone TOF mass analyzer (TOF MS) or as a hybrid quadrupole time-of-fiight (QqTOF) mass spectrometer the latter consists of a quadmpole front-end and an orthogonal acceleration TOF back-end for MS/MS experiments (Fig. 6.10). The orthogonal design minimizes the ions initial velocity spread as they are accelerated into the TOF by a pulsed potential. A QqTOF can be operated as a TOF mass analyzer (QqTOF MS, full-scan) or a quadmpole TOF tandem mass spectrometer (QqTOF MS/MS, product ion scan). Compared to a TOF MS, the... 

Eckers C, Wolff JC, Haskins NJ, Sage AB, Giles K, Bateman R. Accurate mass Uquid chromatography/mass spectrometry on orthogonal acceleration time-of-flight mass analyzers using switching between separate sample and reference sprays. 1. Proof of concept. Anal Chem 2000 72 3683-3688. 

The orthogonal acceleration (oa) feature of a TOF mass analyzer enables it to be used with continuous-beam ion sources [28-31]. The ion beam from the external source enters an ion acceleration region from a direction perpendicular to the main axis of the TOF instrument (see Figure 3.13). A short pulse of an orthogonal accelerating field is applied to eject the ions efficiently in a section of... 

Quadrupole-Orthogonal Acceleration TOF Instrument As of today, quadrupole (Q)-orthogonal acceleration (oa) TOF (oa-TOF) instrument is the most popular hybrid instrument [58,59] a simphstic pictorial representation is shown in Figure 4.11. The quadrupole section consists of a normal massresolving quadrupole and an rf-only quadrupole. The latter serves as a collision cell and as an ion-accumulation device. For precursor-ion scan, the ions desired are mass-selected by the main quadrupole, accumulated in the collision cell, and a packet of the CID product ions is pushed into the TOF analyzer. The precursor-ion selection by the quadrupole is at a medium resolution, but the product-ion analysis by the TOF section is at a reasonably high resolution. 

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