Traditional mass spectrometers used electromagnets to deflect isotopes of different masses which allowed only a certain isotope to reach the detector. But how is the TOF MS different besides the fact that it doesn't use magnets? Does it have a different method of accelerating the ions which leads to them moving with a different velocity? If the methods of acceleration are same wouldn't there initially be no need for magnets to deflect the ions? Or is it the detector that works differently?


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Both types of mass spectrometers separate different chemical species based on the mass-to-charge ratio.

The time-of-flight mass spectrometer (TOF MS) is based on the ions being released at a given instant, such as when struck by a laser, accelerating the ions electrostatically and measuring how long it take for them to strike the cathode target. This is ideal for a lightweight interplanetary or cometary mission such as Rosetta.

Magnetic and quadrupole MS work by bending the beam magnetically or electrostatically so as to spread out the target beam along the width of the target. This is like sending a light-beam through a prism to spread out the spectrum. An advantage of this technique is that it can resolve multiple species simultaneously, but at the expense of fine resolution.

An excellent explanation of TOF and other MS is presented by Young, Waite and Miller.


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