Illustrated Glossary of Organic Chemistry

Nominal mass: In mass spectrometry, an m/z measured or calculated only as an integer.


Glucose
C6H12O6
In the mass spectrum of glucose the nominal mass for M = (6 x 12) + (12 x 1) + (6 x 16) = 180, whereas the exact mass is (6 x 12.0000) + (12 x 1.007825) + (6 x 15.99415) = 180.0588.