Molecular Ion Peak
The peak in a mass spectrum corresponding to the intact molecule after loss of a single electron.
Formula / equation
M⁺·
Unit
Da
In depth
The molecular ion gives the relative molecular mass directly and is normally the highest significant mass in the spectrum. It may be weak or absent if the molecule fragments readily, in which case a softer ionisation method is used to preserve it.
Examples in the real world
Ethanol showing its molecular ion at m/z 46, matching its molecular mass.