Time-of-flight mass analysers

Q-ToF-LC-MS-MS quadrupole time-of-flight mass analyser in combination with (high performance) liquid chromatography and tandem mass spectrometry... 

Figure 3.7 Schematic of a time-of-flight mass analyser, involving the use of a reflectron .

Matrix-associated laser desorption ionization with a time-of-flight mass analyser (MALDl-ToF) was used to examine the crude tryptic peptide mixture from a number of the proteins, without HPLC separation, to provide a mass map, i.e. a survey of the molecular weights of the peptides generated by the digestion process. 

Q-ToF The combination of quadrupole and time-of-flight mass analysers. This allows the m/z ratios of ions produced during a product-ion scan to be measured accurately and the elemental composition of these ions to be determined. 

Reflectron An ion lens nsed in the time-of-flight mass analyser to increase the distance travelled by an ion and thereby increase the resolntion of the instmment. 

Time-of-flight mass analyser A mass analyser in which ions are separated in time as they drift through a field-free flight tube. 

Schematic description of a continuous extraction mode and a delayed pulsed extraction mode in an linear time-of-flight mass analyser, o = ions of a given mass with correct kinetic energy = ions of the same mass but with a kinetic energy that is too high. Delayed pulsed extraction corrects the energy dispersion of the ions leaving the source with the same mjz ratio.

A TOF mass analyser requires a pulsed ion introduction. In an electrospray-TOF combination, the duty cycle is an important issue. A significant improvement in the duty cycle can be achieved in an ion-trap-TOF hybrid instmment the ions from a continuous ion source are accumulated in the ion trap between two ion introduction events. An ion-trap-TOF hybrid instrument was first described by the group of Lubman [68-69]. The system consists of an atmospheric-pressure ion source with a vacuum interface, a set of Einzel lenses, an ion-trap device, and a reflectron time-of-flight mass analyser. The system was applied for fast analysis in combination with a variety of separation techniques [70]. 

Figure 9.8 Schematic of a reflectron time of flight mass analyser. Reflectron lenses act as an electrostatic mirror to both increase the effective length of the flight path, but also to compensate for ion kinetic energy variations (Uq), resulting in higher mass accuracy relative to purely linear time of flight mass analyzers. Consequently, linear time of flight analyzers are nowadays largely obsolete.

Time-of-flight mass analysers, which have been used for many decades, operate on a... 

Fig. 3.5. Schematic representation of a time-of-flight mass analyser with reflectron and external ion storage for time-delay extraction. Ions that enter the field-free drift region migrate to the detector at a rate that is dependent on their m/z ratio. The reflectron lenses compensate for variations in kinetic energies of the injected ions these variations would otherwise produce broadened peaks and loss of spectral resolution.

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