.
The symbolism
[M + H]+
may also be used to represent the protonated molecule. The widely used term 'protonated molecular ion' to describe the
MH+
ion is not recommended, since it suggests an associated product of a proton with a molecular ion.
Source:
PAC, 1991, 63, 1541
(Recommendations for nomenclature and symbolism for mass spectroscopy (including an
appendix of terms used in vacuum technology). (Recommendations 1991))
on page 1550