https://doi.org/10.1351/goldbook.M03752
The abbreviation mz is used to denote the dimensionless quantity formed by dividing the
mass number
of an ion by its
charge number
. It has long been called the mass-to-charge ratio although m is not the ionic mass nor is z a multiple or the elementary (electronic) charge, e. The abbreviation me is, therefore, not recommended. Thus, for example, for the ion (C7H72+) , mz equals 45.5.
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 1544 [Terms] [Paper]