Schematic diagram comparing the time-of-flight of an ion to its initial position in a Bendix Time-of-Flight Mass Spectromter. Time-of-flight mass spectrometry (TOFMS) is a method of mass spectrometry in which an ion's mass-to-charge ratio is determined via a time measurement. As part of the analysis, ions are accelerated by an electric field of known strength, with the velocity of the ion depending on its mass-to-charge ratio. The time that it takes for the ion to reach a detector at a known distance is measured and subsequently used to identify the ion based on its mass-to-charge ratio.