A mass analyzer is used to distinguish minute mass differences while allowing a sufficient number of ions to pass through to produce measurable ion currents.
Resolution of Mass Spectrometers
Resolution is defined as the capacity of a mass spectrometer to differentiate between masses. It is defined as:
- m= the nominal mass of the peak with the lowest mass.
- △m is the mass difference between two adjacent peaks.
Table of Common Mass Analyzers for Mass Spectrometry
|Principle of Analysis
|Deflection of ions in a magnetic field. Ion trajectories depend on m/z value
|Electrostatic focusing followed by magnetic field deflection. Trajectories depend on m/z values.
|Ion motion in dc and radio-frequency fields. Only certain m/z values are passed.
|Storage of ions in space defined by the ring and end cap electrodes. The electric field sequentially ejects ions of increasing m/z values.
|Ion Cyclotron resonance
|Trapping of ions in the cubic cell under influence of trapping voltage and magnetic field. Orbital frequency related inversely to m/z value
|Equal kinetic energy ions enter the drift tube. Drift velocity and thus arrival time at the detector depend on mass.
Reference: Fundamentals of Analytical Chemistry By Douglas A. Skoog, Donald M. West, F. James Holler, Stanley R. Crouch · 2013