ToF mass spectrometry

Relative Atomic Mass (Ar)

The weighted average mass of an atom of an element relative to 1/12th of the mass of an atom of carbon-12.

Relative Molecular Mass (Mr)

The weighted average mass of a molecule relative to 1/12th of the mass of an atom of carbon-12.

Isotope

Atoms of the same element with the same number of protons but a different number of neutrons. (They have identical chemical properties but different physical properties).

Relative Isotopic Mass

The mass of an atom of an individual isotope relative to 1/12th of the mass of an atom of carbon-12.

Mass Number (A)

The total number of protons and neutrons in the nucleus of an atom.

Electron Impact Ionisation

High energy electrons from an electron gun is used to knock out an electron e.g X(g) + e- = X+(g) + 2e-

Electrospray Ionisation

Sample dissolved in a volatile solvent and injected through a fine hypodermic needle connected to a high voltage supply. This causes each particle to gain a proton (H+) from the solvent as it leaves the needle, converting the sample into positive ions. And to gain 1 extra mass.

ToF, 2 ion calculations formula