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The National MagLab is funded by the National Science Foundation and the State of Florida.

Mass Spectrometer (Single Sector)

Mass spectrometers are instruments that give scientists information on the composition of a material. Mass spectrometers can pick apart complex substances and analyze their atoms and molecules by observing how they react to magnetic fields.

This is accomplished by vaporizing the sample, if it’s not already a gas, and ionizing it to give it a charge. Then the mass spectrometer checks how those ions are affected by a magnetic field. The interaction of the ions with the magnetic field gives information on the particle's mass. The particle’s mass in turn can identify what elements the material is composed of. The mass spectrometer sorts and counts these particles, revealing the specimen’s chemical makeup.

The tutorial below shows you what happens to ionized particles as they travel through a Mass spectrometer.


  1. Observe the ions traveling through the Mass Spectrometer. The blue ions are the lightest, the green ions are heavier, and the red ions are the heaviest.
  2. Turn on the instrument’s magnetic field and set it to the lowest field strength. Observe what happens to the heaviest ions when they hit the curve in the tunnel through the magnetic field. Watch the other ions make it all the way to the detector.
  3. Now increase the magnetic field strength to the strongest setting. See which ions make it all the way to the detector.

In order to make it through the curved tunnel of the mass analyzer, the ions need to have just the right mass (and charge) with respect to the pull of the magnetic field, and the geometry and setup of the instrument. Generally speaking: If ions are too “light”, or too “heavy” in their mass-to-charge ratio, they will veer into the wall of the tunnel and never make it to the instrument’s ion Detector. If the ions have just the right mass and charge, the particles travel through the mass analyzer unscathed and reach the detector. The arrival of each ion creates a pulse of electrons and this pulse is recorded.

Depicted is a single sector mass spectrometer. (Scientists also use dual sector mass spectrometers). This technology is widely used in many scientific fields including environmental chemistry, pharmaceuticals, forensic analysis, and even cancer screenings.