What does the time of flight in TOF-MS indicate about the ion?

In Time-of-Flight Mass Spectrometry (TOF-MS), the time it takes for an ion to travel a certain distance is directly related to its mass. The time of flight is influenced by the ion's velocity, which in turn is affected by its mass. Specifically, for ions of a given kinetic energy, lighter ions will reach the detector faster than heavier ions.

The relationship is governed by the principles of motion and energy; the time of flight (t) is proportional to the square root of the mass (m) of the ion when considering its kinetic energy. This means that if you were to observe the square of the time of flight, it would be proportional to the mass of the ion, providing a basis for mass determination using the TOF measurement.

Thus, the correct understanding is that the time of flight helps to determine the mass of the ion, establishing a proportional relationship between mass and the square root of flight time. This principle is fundamental in TOF-MS, allowing for effective mass analysis of ions based on their time of flight.