Mass Spectrometry

Glossary of Terms - Content

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  1. Mass Spectrometry
  2. Sources of Ions
  3. Analysers
  4. Linear Analysers
  5. Trap Analysers
  6. Multi-Analyser Configurations
  7. Detectors
  8. Spectra
  9. Sample Introduction
  10. Additional Resources
Analysers Linear Analysers, Trap-Analysers and Multi-Analysers
Single Focussing A magnetic field alone is used to separate ions according to their m/z ratios (strictly, according to their momenta).
Double Focussing A combination of electrostatic (E) and magnetic (B) fields is used to compensate for variations in the energies of the ions formed in the source and thence to improve the resolution (qv) of the analyser. (see also forward and reverse geometry).

B

The term used for the magnetic field.

E

The term used for the voltage in an electrostatic analyzer. 

Q

The abbreviation for a quadrupole analyser. 

q

 The abbreviation used for an Rf only quadrupole collision chamber

V
Accelerating Voltage

 The voltage applied to the source to accelerate the ions formed into the analyser.

Scanning

 Magnetic instruments are scanned by varying either the magnetic field or the accelerating voltage.

Linked Scans

 Specialised scans where functions of B and E are varied (see below).

Quadrupole(Q)

 The application of a combination of DC and AC voltages to four parallel rods creates a filter through which, on application of the appropriate voltages, only ions of any one defined m/z value can be transmitted. If only an Rf field is applied all ions are transmitted (q).

Time-of-Flight (TOF)

 The ions formed are all accelerated by a pulsed potential down an evacuated tube (drift region) and their time of arrival at a detector is determined. This is a function of their m/z values.

Reflectron TOF

 The ions passing down a TOF analyser are reflected by an electrostatic mirror; this focusses ions of varying kinetic energy, but identical m/z, leading to higher resolution.

DE TOF
(Delayed Extraction Time-of-Flight)

 A technique in MALDI-TOF mass spectrometry in which improved resolution is obtained by applying a controlled delay between ion formation and acceleration.

PSD
(Post Source Decay)

 Describes the controlled fragmentation processes which occur in TOF in the drift region of the analyser.
Orthogonal TOF The ion beam is analysed by TOF in a direction orthogonal (at right angles) to its original formation.
Hexapole A small six rod device used to focus a divergent beam of ions.

 

 

 

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