Illustrated Glossary of Organic Chemistry
Nominal mass:
In
mass spectrometry
, an
m/z
measured or calculated only as an integer.
Glucose
C
6
H
12
O
6
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.
Related terms:
Mass spectrometer
,
molecular ion
,
M+1
,
M+2
,
fragment ion
,
electron impact ionization
,
EI
,
chemical ionization
,
CI
,
MALDI,
gas chromatography-mass spectrometry
,
GC-MS
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